How Los Angeles Sprawled, 1781–2020: An Animated Map

Half of It Since 1957

On 4 September 1781, 44 settlers from Sonora and Sinaloa founded El Pueblo de Los Ángeles beside a river in a dry coastal plain. By the 2020 census the urban areas that grew out of it, from Camarillo to Hemet and from Lancaster to Temecula, held 17.4 million people on almost 8,000 km² of land (the five counties of the region, desert included, count 18.6 million). The property records behind this map put the midpoint of that growth surprisingly late: half of the ground that carries a building today had its first one by 1957, and the other half has been added since.

The map shows that growth as it happened. Every built-up area takes the colour of the era of its first building: dark red for the pueblo and the railroad towns, orange for the streetcar suburbs and the 1920s, green and blue for the postwar tracts and freeway suburbs, purple for the exurbs. It reads like the rings of a tree that grew along rail lines and freeways and jumped over mountain ranges. The data stop with the buildings on record in 2020.

Pueblo, Missions and Ranchos (1781–1876)

The pueblo was not the first Spanish settlement in the region: Mission San Gabriel dates from 1771 and Mission San Juan Capistrano from 1776. For almost a century Los Angeles stayed a small town among cattle ranchos, and the first US census, in 1850, counted 1,610 people. A handful of other towns came before the railroad: San Bernardino (1851), Anaheim (1857), Phineas Banning's port of Wilmington (1858), Riverside, Pasadena and Santa Monica. On the map they are small dark patches. Almost no building of that age survives in the property records, so this first era is the one part of the map drawn from documented town sites and not from the data.

Railroads and the Boom of the Eighties (1876–1901)

On 5 September 1876 the Southern Pacific line from San Francisco reached Los Angeles. When the Santa Fe arrived as a competitor in 1885, a fare war followed that for one day cut the ticket from the Midwest to a single dollar. Settlers and speculators came by the trainload, dozens of townsites were staked out along the two lines, and the boom peaked in 1887 before it collapsed the year after. Many paper towns vanished, but the people stayed: the city went from 11,183 inhabitants in 1880 to 102,479 in 1900. On the map this is the red core of Los Angeles and Pasadena and a scatter of red dots along the railroads: 182 km² of ground in 25 years.

Red Cars, Water and the Twenties (1901–1929)

In 1901 Henry Huntington incorporated the Pacific Electric Railway. Its 'Red Cars' grew into an interurban network of more than a thousand miles of track, and its real business was land: wherever the line went, lots were sold. The orange areas on the map are the suburbs those lines opened. Water was the other limit. On 5 November 1913 the Los Angeles Aqueduct delivered Owens Valley water at the northern end of the San Fernando Valley, and in 1915 most of that valley joined the city to get it, which more than doubled the city's area.

Then came oil (Signal Hill, 1921), film and the car. The city's population more than doubled in the decade, to 1,238,048 in 1930, and the car let builders fill the gaps between the rail lines. In the mid-1920s new ground was built on at almost 90 km² a year. The Hollywood sign dates from that peak: it went up in 1923 as 'Hollywoodland', an advertisement for a hillside housing tract. By the Wall Street crash of October 1929, 23% of today's dated ground had its first building.

Depression, War and the Tract-Home Boom (1930–1961)

The crash shows in the records at once: in 1931 to 1934 new ground was built on at about 20 km² a year, less than a quarter of the rate of the mid-1920s. The Arroyo Seco Parkway to Pasadena, dedicated on 30 December 1940, was the first freeway in the West, but the war held building back once more while aircraft plants and shipyards drew hundreds of thousands of workers to the region.

After 1945 the pent-up demand was released, and by 1953 to 1956 about 117 km² a year was being added. In Lakewood about 17,500 houses went up between 1950 and 1953, and the method was copied across the basin. The buyers paid with mortgages insured by the federal FHA or, for veterans, the VA, and for years lenders and builders kept most of the new tracts white; from 1956 the federal Interstate programme also paid nine-tenths of the cost of the freeways that became Interstates. Disneyland opened among the orange groves of Anaheim on 17 July 1955, and Orange County grew from 216,224 people in 1950 to 703,925 in 1960. The era from 1946 to 1961 accounts for 24% of all dated ground: the large green area that fills the basin from Northridge to Torrance, West Covina and Garden Grove. It ends on 9 April 1961, when the last Red Car ran to Long Beach.

Freeways, Master Plans and the Outer Edge (1962–2020)

With the basin nearly full, the freeways carried the suburbs outwards (blue on the map): down the Orange County coast, into the hills at Diamond Bar and Mission Viejo, west into the Conejo and Simi valleys and north over the mountains to Valencia, a planned town started in 1967. The University of California opened its Irvine campus in 1965, at the centre of a master-planned new town on a cattle ranch. New ground was still being built on at about 67 km² a year when, on 6 June 1978, California's voters passed Proposition 13 and capped the property tax.

The next ring (dark purple) is the exurbs of the 1980s, from Moreno Valley and Temecula in the Inland Empire to Palmdale in the high desert, with a peak of almost 90 km² a year in the late 1980s that the recession of the early 1990s cut to about 30. The last wave (light purple) came in the early 2000s, at about 61 km² a year: Menifee, the old dairy land around Eastvale and the former El Toro air base in Irvine. It ended with the housing crash of 2008. In 2009 to 2012 only about 8 km² a year got a first building, and by 2008, 98% of today's dated ground had been built on.

After the Edge

Seen from the edge, the sprawl has all but stopped, for plain reasons: it has reached the mountains, the desert and the limit of a bearable commute. Since 2008 new homes have mostly gone up on ground that was already built on, as apartments on old lots and small units in back yards, which is why the housing fights of today's Los Angeles are about density rather than new tracts. And the region is denser than its reputation: by the Census Bureau's measure for 2020 the Los Angeles–Long Beach–Anaheim urban area, with 12.2 million people at about 7,500 per square mile, is the most densely populated large urban area in the United States, ahead of San Francisco–Oakland and New York.

On the map Altadena, at the foot of the San Gabriel Mountains, carries the dark orange of the streetcar suburbs, and Pacific Palisades, on the bluffs above the ocean, the amber of the 1920s. Both burned in the Eaton and Palisades fires that began on 7 January 2025, after the map's last frame, and thousands of homes were lost in neighbourhoods a century old.

How to Read the Map

Each colour is an era, and an area keeps the colour of the era in which it got its first building. The nine eras end at turning points rather than round years, from the railroad (1876) and the crash (1929) to Proposition 13 (1978) and the 2020 census, and within an era the colour fills in over two or three dated steps. Eleven pins tell the events behind each wave, from the pueblo to the Inland Empire's boom and crash; smaller dots mark the rest, such as Signal Hill, the Colorado River Aqueduct (1941) and the State Water Project (1973).

This is a map of first buildings, not of population or density. The year is that of the oldest building still on record, so districts that were cleared and rebuilt (downtown and Bunker Hill above all) look younger than they are, and one ranch house can date a 250-metre cell decades before the tract around it; the map is therefore smoothed to about a kilometre, and an area changes colour once roughly half of it is built. About a fifth of the land has no dated building (airports, ports, industry, parks) and takes the era of its nearest dated neighbour; mountains and open space are blank. The last frame fills the 20 urban areas the map draws. The Oxnard–Ventura urban area in the west and the Coachella Valley in the east are not drawn, although both count towards the 18.6 million of the five counties (Los Angeles, Orange, Riverside, San Bernardino and Ventura).

How the Map Was Made

The years come from HISDAC-US, the Historical Settlement Data Compilation for the United States: version II of its first-built-up-year layer (Ahn, Leyk, Uhl and McShane, Harvard Dataverse, doi:10.7910/DVN/HHFM5E), which gives the year of first settlement for every 250-metre cell of the conterminous United States from property and parcel records. The same dataset covers every city in the country, so the same map can be made for Phoenix, Houston or Atlanta. The outline of the region is the set of 20 urban areas of the 2020 census in and around the Los Angeles basin, from the Census Bureau's TIGER files, with 17.4 million inhabitants on 7,980 km².

For each of the 23 dates the cells built by that year were smoothed over about 400 metres and cut as one mosaic, so that neighbouring eras share exactly the same border. The areas quoted in this article are counts of 250-metre cells by the year of their first building: ground that has been built on, not the footprint of the buildings.

Chronological Timeline

• 4 September 1781 — El Pueblo de Los Ángeles founded by 44 settlers
• 5 September 1876 — The Southern Pacific railroad arrives
• 1901 — Pacific Electric's Red Cars
• 5 November 1913 — The Los Angeles Aqueduct opens
• October 1929 — Wall Street crash; the city has 1.2 million people
• 1950–1953 — About 17,500 houses built in Lakewood
• 17 July 1955 — Disneyland opens in Anaheim
• 9 April 1961 — The last Red Car runs to Long Beach
• 6 June 1978 — Proposition 13 caps property taxes
• 14 July 1990 — The Blue Line to Long Beach opens: rail returns
• 2008 — The housing crash stops the outer edge
• 2020 — Census: 17.4 million in the urban areas on the map, 18.6 million in the five counties
• 7 January 2025 — The Eaton and Palisades fires (after the map's last frame)