Arpent

Unit of length

There were various standard arpents. The most common were the arpent used in North America, which was defined as 180 French feet (pied, of approximately 32.48 centimetres or 12.79 inches), and the arpent used in Paris, which was defined as 220 French feet.

Unit of area

Historically, in North America, 1 (square) arpent (arpent carré), also known as a French acre, was 180 French feet × 180 French feet = 32,400 French square feet = about 3419 square metres = about 0.845 English acres. Certain U.S. states have official definitions of the arpent which vary slightly:

In Paris, the square arpent was 220 French feet × 220 French feet = 48,400 French square feet, about 5,107 square metres or 1.262 acres.

Louisiana

In Louisiana, parcels of land known as arpent sections or French arpent land grants also pre-date the Public Land Survey System (PLSS), but are treated as PLSS sections. An arpent is a French measurement of approximately 192 feet (59 m), and a square arpent (also referred to as an arpent) is about 0.84 acres (3,400 m²).

French arpent land divisions are long narrow parcels of land usually found along the navigable streams of southern Louisiana, and also found along major waterways in other areas. This system of land subdivision was begun by French settlers in the 18th century, according to typical French practice at the time and was continued by both the Spanish and by the American government after the acquisition of the Louisiana Purchase. A typical French arpent land division is 2 to 4 arpents wide along the river by 40 to 60 arpents deep, while the Spanish arpent land divisions tend to be 6 to 8 arpents wide by 40 arpents deep.

This method of land division provided each land-owner with river frontage as well as land suitable for cultivation and habitation. These areas are given numbers just like standard sections, although the section numbers frequently exceed the normal upper limit of 36.