Studying the Ownership Structures of an Algiers’ Neighbourhood on the Eve of Its Demolition. The Creation of a Geographic Information System Using Historical Land Records from the 1930s

(1) Introduction

This article presents a published dataset that provides insight into the structure of property ownership in a colonial context. The demolition of the Marine district in Algiers, at the bottom of the Casbah, began in the late 1920s.¹ The buildings, constructed before the conquest (1830) or in the decades that followed, were considered particularly unsanitary. The municipality decided to demolish and then have it rebuilt by the highest bidder: the Régie foncière de la ville d’Alger (RFVA) won the contract at the end of March 1931. This estate authority was founded by the Compagnie nouvelle foncière et financière (established by the Banque de Paris et des Pays-Bas in collaboration with Crédit Lyonnais) and the Crédit foncier d’Algérie et de Tunisie. Demolishing and then rebuilding requires, first of all, the expropriation of all property owners.

It was this need for expropriation that led to the creation of two sets of documents enabling a study of property ownership in a neighbourhood of Algiers in the 1930s, an approach that remains unprecedented:

• -  a cadastral map of the neighbourhood (Doc. 1). This map is preserved in the archives of BNP Paribas, the banking group that succeeded the Banque de Paris et des Pays-Bas.² Such a plot-level representation is extremely rare among the sources used to write the history of Algeria in the 20th century.

  

  Doc. 1

• -  a set of prefectural decrees required for the expropriation process (Doc. 2) published in the Journal officiel de l’Algérie (JOA). These decrees, the context in which they were issued, their content and their limitations are described below. A diagram summarising all the procedures leading to the expropriations has also been produced (Figure 1). This includes links to regulatory texts (decrees outlining the procedure, municipal resolutions, prefectoral orders), all available on Gallica. The data structure only covers decrees initiating a public utility inquiry (1st stage) and not those declaring the expropriation to be in the public interest (2nd stage) or the expropriation orders themselves (3rd stage).

  

  Doc. 2

Figure 1

This corpus is unique in two respects: on the one hand, it covers an entire neighbourhood rather than isolated buildings; on the other, it helps overcome the challenges associated with municipal archives in Algerian cities, such as poor preservation (Guillopé, 2024).

These documents have been processed—involving the data entry of expropriation orders and the vectorisation of maps—to create a geographic information system. Over the past quarter-century, this approach has been used to re-examine numerous urban areas like Paris or Shanghai (Noizet, 2006; Pinol, 2009; Mou, 2012). Algiers, however, had not yet been studied in this way. The data (spreadsheets and maps) presented here thus aim to enrich the history of Algiers through the use of geomatics.

This map and these decrees enable us to reconstruct the state of land and property ownership in the neighbourhood on the eve of its destruction. The plot numbers listed in the prefectural decrees can be cross-referenced with the plots shown on the map, thereby allowing the information contained in the prefectural decrees to be mapped.

For the publication of this dataset, the cadastral map was georeferenced and then vectorised using QGIS software.³ The information contained in the prefectural decrees was entered into a spreadsheet: it is this data entry process – the choices made, the methods used, the coding, etc. – that is the subject of this article, as the process was by no means straightforward. Transforming these sources into data forms the basis, for the early 20th century, of both a situated social history of Algeria and a spatial history of property in Algeria.

This dataset is briefly described (2). Then, we offer some reflections on the scope of the corpus and the conceptual model of the database created to digitise and link the map to the prefectural decrees (3). Finally, we conclude by discussing the potential uses of this dataset and the new approaches to history it enables (4).

(2) Dataset description

Repository location – DOI: 10.34847/nkl.cd4cmpof

Repository name – Nakala (a data repository that aims to preserve and disseminate data produced by French research projects in the Humanities and Social Sciences).

Object name – Studying the ownership structures of an Algiers’ neighbourhood on the eve of its demolition. The creation of a geographic information system using historical land records from the 1930s.

Size – eight lines for historic buildings (edifices_historiques), 558 lines for plots (parcelles), three lines for sources, 602 lines for buildings (batiments), 820 lines for property owners (proprietaires), 901 lines for parcel-owner relationships (parcelle_proprietaire), 83 lines for municipalities of residence, 63 lines for the variable dictionary

Format names and versions – .gpkg, .ods.

Creation dates – 2026.

Dataset creators – Thierry Guillopé, Thibault Lecourt, Nicolas Massot.

Language – French (language of historical sources transformed into data).

License – Creative Commons Attribution Non Commercial 4.0 International (CC-BY-NC-4.0).

Publication date – 2026-09-08 (version 2).

(3) Method

(3.3) Relational database modelling

We have digitised this archive data into a spatial relational database model (Figure 2). Two tables were created based on the vectorised map, in geopackage format (.gpkg):

• edifices_historiques: listed buildings in the public domain (not registered in the land registry) and historic monuments

• parcelles: land plots

Figure 2

Five tables were created based on the decrees, in a spreadsheet format (.ods) to facilitate its reuse:

• sources_joa: the official gazette corresponding to the information gathered

• batiments: about buildings plot

• proprietaires: about owners

• parcelle_proprietaire: matching of plot(s) and owner(s)

• communes_residence: municipality of residence of the owners (communes_residence)

In the spreadsheet, a dictionary of variables completes this set of tables.

All the information contained in these orders is derived from the cadastral roll records. Where these records were unusable (confusing, outdated, illegible, etc.), the public inquiry officer (or a prefecture employee) gathered information on the property owners, likely by visiting the site. If the source presents information derived from both the role records and from an information gathering (e.g., Doc. 3, plot no. 18), only the latter was entered, as it was deemed more up-to-date.

Doc. 3

We determine the ‘sex’ based on the first name and/or civil status designations (‘Mrs’, etc.).

In the communes_residence table, the codes for Algerian municipalities refer to the geolocated database of municipalities in colonial Algeria compiled in previous research (Guillopé & Lecourt, 2022). The other codes refer to the nomenclature officially used in each country. These correspondences enable the municipalities of residence of property owners to be mapped using GIS software.

(3.4) A myriad of specific cases that pose data entry problems

(3.4.1) Incomplete addresses for which a local authority has been designated

Example:

Doc. 4

→ In this case, an address has been assigned to these owners based on existing evidence. In most cases, ‘Algiers’ was chosen. The addresses assigned in this way are noted in the ‘comments’ column of the relevant table.

(3.4.2) Reference to a female owner listed under her husband’s name, who is usually deceased

Example:

Doc. 5

→ There are at least two pitfalls to avoid here:

• -  treating ‘Vincent Dourso’ as the owner when it is in fact his widow, ‘Silvia Pinto’, who is the owner.

• -  omitting part of the information by failing to note the family connection – in this case, the marital one –; yet this may be of significant historical interest.

To handle this scenario, we have chosen to create a ‘marital status’ (statut_marital) column and a ‘spouse_id’ (id_époux) column: the first indicates whether the person is a widow or widower or has a deceased spouse, whilst the second indicates the unique identifier (owner_id / id_proprieteaire) of the husband or wife, each of whom represents a row in the owners table. From a conceptual point of view, this approach involves modelling a lookup table that links the owners table to itself, thereby enabling two individuals to be linked together. Some individuals in this table may therefore not own any plots of land, but may be the spouse of an owner, as in the example given above.

(3.4.3) Management of complex building areas

Example 1:

Doc. 6

Example 2:

Doc. 7

→ Generally speaking, the sources provide, for each parcel, the cadastral identifier of the building located on it and the cadastral area of that building. If there are multiple buildings on the parcel, there will be multiple lines corresponding to the same parcel. Most often, a single area is listed for the parcel, which in all likelihood corresponds to the total built-up area. This value is entered in the “surface_batie” field of the parcel table. However, in some cases, an area is listed for each building. In such cases, our modeling approach was to sum the built-up areas on the same parcel. When the built-up area is listed as “totalité” (totality) in the sources, we assume that the entire area of the parcel is built up. In this case, the “surface_batie” field in the parcel table takes the value of the parcel’s geodetic area, calculated using QGIS based on the vectorised parcel geometry and the SCR Nord Sahara 1959/UTM Zone 31N coordinate system. Some inconsistencies arise, with the built-up area turning out to be larger than the geodetic area of the parcel. In most cases, these inconsistencies are less than 100 m² and can be attributed to inaccuracies in the vectorisation and the geodetic calculation of the area. For three parcels, however (409, 42, and 229 BIS), these discrepancies are 508 m², 199 m², and 144 m², respectively—these are likely errors in the source data.

(3.4.4) Link between plot and owner via a bracket

Doc. 8

→ This is a unique situation. In view of this, and given the need to clarify this information, it was noted in the table of owners, in the ‘comments’ column, that the two owners were linked by a brace. As this symbol was unclear, it was disregarded.

(3.4.5) Mention of the nicknames of certain individuals

Doc. 9

→ The nickname has been entered in the ‘comments’ column of the ‘owners’ table.

(3.4.6) Confusing information that has been ‘corrected’

In cases where the information in the sources used is unclear (decisions to launch a public inquiry, i.e., the first stage of the expropriation procedure)…

Doc. 10

→ …we have chosen to refer to the information set out in the order declaring the expropriation of such-and-such a plot to be in the public interest (i.e., the second stage of the expropriation procedure). In this case, this approach enables us to confirm that the correct information is as follows:

Doc. 11

(3.4.7) No owner for a plot of land

Doc. 12

→ In this case, we have noted in the ‘comments’ column of the ‘owners_plots’ (parcelle_proprietaire) table that the source does not mention an owner. The ‘owner_id’ (id_proprietaire) column remains blank.

(3.4.8) Two names of owners appear to refer to one and the same person

Doc. 13

Doc. 14

→ Given the slight uncertainty as to whether this refers to one and the same person – in two different orders – two different owners were named. In this case:

• -  id_proprietaire No. 42 (‘M. W. Oualid, 9 bis, rue Pérignon, Paris’, plot 24)

• -  and id_proprietaire No. 383 (‘William Oualid, 9 bis, rue Pérignon, Paris’, plot 286)

• …are listed on two lines in the table of owners.

• → A reference to this probable redundancy appears in the ‘comments’ column of the ‘owners_plot’ (parcelle_propriétaire) table and the ‘owners’ (proprietaires) table.

(3.4.9) Converting the surnames of Algerian men and women into data

Full North African names consist of six elements⁴ (Larcher, 2013; Ageron, 2010; Sublet, 1991):

• -  the given name (ism).

• -  the lineage (nasab), commonly reduced to the father’s name preceded by the term ‘ben’ (for sons) or ‘bent’ (for daughters).

• -  a name of territorial or ethnic origin (nisba).

• -  a term referring to a person’s firstborn child (kunya), less common in the Maghreb than in the Mashreq.

• -  a nickname (laqab).

• -  possibly an honorific title (Hajj, Sidi, Si…).

This naming convention does not conform to the French standards that were introduced during the colonial period. It was therefore decided to organise the names in the table of owners into three columns:

• -  Surname: assigned to everyone; the abbreviation ‘SNP’ (Sans nom patronymique, i.e., ‘no surname’, used by the French authorities) has been added by us.

• -  First name: assigned to everyone

• -  The full names appearing in the sources have been reproduced in full in the ‘comments’ column in order to preserve their accuracy and detail.

(4) Applications and implications

This dataset makes it possible to examine the property at a specific moment—the years marking the Centenary of the colonisation of Algeria—rather than to define a trajectory. It forms the basis for a wide range of future analyses incorporating the spatial dimension of land ownership. It allows for the mapping of an individual’s holdings or the locations of property owners—who often hailed from Algiers, though many came from metropolitan France or resided in Morocco and Tunisia. The city’s significant land holdings can be highlighted right away: the municipality and the Compagnie nouvelle foncière et financière owns 70 parcels, representing close to 17% of the total area. It is also possible to conduct analyses based on gender, which is largely known. The occupation of property owners is known in fewer than 1 in 10 cases; therefore, it is necessary to explore other sources to provide analyses related to their social status.

Research into both property owners and the Marine neighbourhood can draw on a wide variety of sources, many of which can also be organised into datasets.⁵ To name a few: lists of owners⁶ and lists of retailers;⁷ civil status record⁸ or military conscription forms,⁹ two sources digitised by the Archives nationales d’outre-mer (Aix-en-Provence); files relating to expropriations in the archival collection ‘Interior and Fine Arts’ (‘Intérieur et Beaux-arts’, 15E, ex-IBA) from the National Archives of Algeria and that of the ‘Administrative Court’ (7K) from the Archives of Algiers’ wilaya; land registry records (Guignard, 2015); municipal archives (Belmadoui & Boukemiche, 2008); press, extensively digitised on the Gallica platform.¹⁰ All in all, it would be possible to piece together the entire history of a key part of life in Algiers up until the mid-20th century.

Finally, it is worth noting that this dataset lends itself to fruitful cross-referencing with other datasets: those compiled, for example, by Thierry Guillopé as part of his PhD research on social housing in Algeria from the 1920s to the 1960s should provide a better understanding of the factors shaping residential trajectories.¹¹ Cross-referencing these sources and data in this way will enhance both the depth of our understanding and our ability to analyse the issues, thereby shedding light on social and urban dynamics through spatial and historical analyses of land ownership.

Author Contributions

Thierry GUILLOPÉ: Conceptualization, Data curation, Formal Analysis, Investigation, Methodology, Writing – original draft.

Thibault LECOURT: Conceptualization, Data curation, Formal Analysis, Investigation, Methodology, Writing – review & editing.

Nicolas MASSOT: Data curation, Methodology.