Detroit was the Silicon Valley of the late 19th and the first half of 20th century. The city grew into a hub of commerce and industry spread along Jefferson Avenue, with multiple manufacturing firms taking advantage of the transportation resources afforded by the river and a parallel rail line.
Around the start of the 20th century, numerous entrepreneurs in the Detroit area forged into a production of the automobile, capitalizing on the already-existing machine tool and coach-building industry in the city. A thriving trade set the stage for the work of Henry Ford, whose automobile Highland Park Ford Plant in 1910 revolutionized not only automobile manufacturing but virtually created the concept the assembly line and mass production.
Historic Gilded Age gave rise to upscale neighborhoods, including the Boston-Edison, Indian Village, and Palmer Woods. In 1930s, with the factories came high-profile labor unions. The labor activism during those years increased the influence of union leaders in the city such as Jimmy Hoffa of the Teamsters and Walter Reuther of the Autoworkers.
The city became the 4th-largest in the nation in 1920, after only New York City, Chicago and Philadelphia, with the influence of the booming auto industry. The Great Depression was devastating for Detroit, as sales of automobiles plunged and there were large-scale layoffs at all industrial enterprises. Major Murphy insisted that no one would go hungry, and set up the Mayor's Unemployment Committee that set up relief soup kitchens and potato gardens.
From 1942 to 1945, production of commercial automobiles in the city ceased entirely, as its factories were used instead to construct M5 tanks, jeeps, and B-24 bombers for the Allies. By 1945, Detroit was running out of space for new factories. The postwar years 1945-70 brought high levels of prosperity as the automobile industry had its most prosperous quarter-century.
Detroit, like many places in the United States, developed racial conflict and discrimination following rapid demographic changes as hundreds of thousands of workers were attracted to the industrial city. In the 1970s and 1980s dozens of violent street gangs gained control of the city's large drug trade, which began with the heroin epidemic of the 1970s when the crimes became increasingly more destructive. Hundreds of vacant homes across the city were set ablaze by arsonists. The number of fires was reduced only by razing thousands of abandoned houses - 5,000 in 1989-90 alone.
In the late 1980s and early 1990s, the city began to experience a revival, much of it centered in Downtown, Midtown, and New Center.