History of Transportation in Los Angeles
Since 1873, different systems of transit have served the greater Los Angeles region. During this period, there have been different private and public companies to operate transit systems including steam railroads, cable cars, electric streetcars, interurban trolley buses, bus rapid transit, mass rail transit, and commuter rail. In addition to public transportation, the city and county of Los Angeles, and its surrounding metropolitan region, have heavily made use of the automobile and its expansive network of freeways.
Early Railroads and Railways: 1870s
Postcard of the Southern Pacific Railroad, (Source: USGW archives)
The beginning of Los Angeles’ history as a city is in large part due to the construction of a railroad connection to the East, about a century after the founding of the Spanish settlement of El Pueblo. With the completion of the transcontinental railroad, Los Angeles transformed from a small, isolated agricultural town into one of the world’s prominent metropolises. The completion of the Southern Pacific rail line from San Francisco in 1876 marked the emergence of Los Angeles as the urban core of the southern California region. The city’s superiority was reinforced by two direct rail lines with the East: the Southern Pacific in 1881 and the Santa Fe in 1885. 
These two railroads heavily contributed to the great population boom of the 1880s, when the first great influx of migrants from across the country settled into the greater Los Angeles region. The first railroads not only followed the traditional routes that had been taken by Native Americans and Mexicans, but also became the pivotal axes for ongoing settlement. In 1869, Robert Widney founded the East Los Angeles and San Pedro Railroad line to connect the Wilmington wharves to the city. Three years later it was offered to the large rail company, the Southern Pacific as a part of their transcontinental rail line to Los Angeles. The Southern Pacific set up another line in 1877 to enter the city from the only north entrance, through the San Fernando Valley along the Los Angeles River. Southern Pacific further enforced its reputation with the completion of an eastern link, passing through Pomona and Ontario and connecting with Texas. The second large rail line, the Santa Fe, entered Los Angeles through the San Gabriel Valley, moving past Pasadena on its journey downtown. These two major railroad companies continued to extend local routes throughout the 1870s and 1880s, with smaller independent lines. The Southern Pacific continued opening a line to Anaheim, while the Santa Fe expanded further south to San Diego. 
Several new towns and smaller cities emerged in the process of railroad construction by the two companies. The railroads were not only the cause of the population boom, but the physical location of the lines also served as the basis for the place of new settlements by bringing new migrants into the area. While most of these boomtowns that parallel the Southern Pacific and Santa Fe railroads failed, more than thirty survived to provide the core of growth in Los Angeles that is evident to this day, including: Alhambra, Arcadia, Burbank, Claremont, Covina, Fullerton, Gardena, Glendale, Hollywood, Inglewood, Redondo Beach, South Pasadena, Watts, and Whittier. 
Red and Yellow Cars - The Streetcars of Los Angeles
Not long after the completion of the railroads, private developers completed the first electric trolley and streetcar lines in 1887 to promote real estate in Los Angeles. In the following decade and a half, many electric streetcar lines were added to Los Angeles and surrounding cities, with electric interurban streetcars to connect the cities. By 1911, Southern Pacific consolidated the entire electric interurban streetcar network of Los Angeles and operated it as the Pacific Electric Railway Company, whose cars were known as “Red Cars”. Around the same time, the Los Angeles Railway operated a local system of streetcars in central Los Angeles, known as the Yellow Cars. By 1925, these railways provided the greater Los Angeles metropolitan region the largest trolley system in the world. From the early to mid-1900s, the electric streetcar became the most popular mode of transportation in the Los Angeles region, taking over the popularity of railroads. 
Pacific Electric lines in "streetcar suburbs",
(Image copyright Pacific Electric Railway Historical Society, peryhs.org)
(Image copyright Pacific Electric Railway Historical Society, peryhs.org)
The streetcar system was a crucial mechanism in promoting the spread of population throughout Los Angeles in the 20th century. Streetcars allowed residents and new visitors to travel throughout greater Los Angeles and into the new suburbs that were forming around the area, soon to be popularized as “streetcar suburbs”. Trolley cars became a common sight in most early suburban neighborhoods, as few streets were more than six blocks from a rail line. In the first decade of the century, when the electric trolley virtually held a monopoly of intercity transportation, Los Angeles witnessed one of the largest population booms of the century, as suburbs in the outlying areas of the San Fernando Valley and Orange county quickly emerged in succession. Electric railway provided a cheaper means for the movement of people, but most businesses and industry remained centered around the downtown Los Angeles area. Central Los Angeles never retained a dense urban core for residents, but instead became an expansive metropolis of single-family neighborhoods. Since the conception of the trolley system by private developers, streetcars played a crucial role in expanding and developing the residential patterns of the region. The extensive system of electric railway allowed the growing population to combine an urban economy of production and consumption with a more rural environment of open landscape and community. 
The Automobile Era
The era of railway construction had come to an end with the beginning of the automobile age, with the emerging development of the single-family tract houses. Existing interurban trolley and railway lines already provided the base for the pattern of suburb communities, and easily facilitated the shift to the automobile. This single-family pattern of post-war housing construction quickly made the Los Angeles region dependent on private automobile transportation. The automobile permitted further flexibility to settle in an area that could be cleared for a road, which resulted in settlements in more remote locations in the periphery of Los Angeles that were not previously served by trolley lines.  From the 1920s onwards, automobile registration increased at an average rate of 45,000 vehicles a year. The automobile had finally become the indispensable form of transportation in Los Angeles. The decentralization of residential population eventually also led to the beginning of decline of the central business district and the decentralization of industry. Though railway construction had ended, private rail companies like the Pacific Electric began to look to buses for public transit to serve new routes and also to compensate for the less profitable trolley lines. The steady conversion of rail lines to bus routes allowed mass transit to continue with the adoption of automobiles and streets.
Post War Creation of Freeways
Early highway map in the greater Los Angeles region,
A master plan for freeways in the Los Angeles region was introduced in 1947, and construction began in the 1950s. This transportation network was the final product of previous generations of transportation systems that have been placed onto the southern California landscape, including early Native American and Mexican colonial trails, steam railroads, electric streetcars, and automotive highway. Los Angeles’ dependence on the automobile and freeways comes as a product of the region’s widespread urban form. Alongside the natural landscape of the mountains and rivers in influencing the organization of the metropolis, the freeway system is undeniably the single most important element of the man-made landscape. Consequently, the concept of the freeway system for Los Angeles was designed to serve a prevalent pattern of decentralized, low-density development. Almost two decades later of the freeways were completed in the 1960s and 1970s. While their long-term effects were not felt immediately, freeways quickly became the dominant mode of urban traffic, remaining crowded since the time of completion. Though only occupying an insignificant portion of land in the Los Angeles area, freeways dominate the physical and psychological landscape, serving as the primary means of connection between the region’s numerous nodes, towns, suburbs, and neighborhoods. 
Revival of Mass Transit
In 1951, the Los Angeles Metropolitan Transit Authority (LAMTA) was formed as a public transit planning agency for the region. It subsequently took over and operated the existing privately owned bus lines along with the former streetcar and railway lines. By the late 1950s and early 1960s, the former streetcar system was finally closed and removed, leaving the freeway system and automobiles as the dominant mode of transportation and buses as the only form of public mass transit. In 1964, the Southern California Rapid Transit District (SCRTD) emerged from an act created by the California State Legislature and superseded the LAMTA, with a goal to improve the existing bus networks and create an efficient transit system for the greater Los Angeles region. Counties served include Los Angeles, Orange, Riverside and San Bernardino.