World War II changed the town of San Pablo forever. In just a few years, the population boomed from 2,000 to 25,000 people, due to the jobs at the Richmond Shipyard. People came from all over the United States to get jobs as welders. Many African Americans came from the South, and established the first sizable black community. Housing was put up as quickly as possible to accommodate these new workers. Many of these tiny homes on small lots that characterize San Pablo were built during the war. Not all of them were intended to be permanent buildings, and had shoddy construction.

San Pablo kept up its reputation as a party town - nightclubs and dance halls featuring country swing bands were popular among the young shipyard workers. The clubs were often open 24 hours a day to accommodate all three work shifts at the shipyard.

After the war, many people decided to stay in San Pablo, and the town needed to take the step of incorporating into a city. On April 27, 1948, the residents voted to create a city government. The first mayor was J.H. Crawford.

Sidewalks

The war had changed San Pablo into a suburban city. The last dairy ranchers sold out to giant corporations, and the last farmers divided and sold their land for housing tracts.

The post-war community settled down to raise families. In the 1950s public works projects paved the streets, added sidewalks and installed streetlights. Playgrounds were opened, a hospital was built, Contra Costa College opened, shopping centers replaced wartime housing. Gambling was outlawed.

In 1976 San Pablo won the All America City Award for civic improvement projects.

The Alvarado Square Civic Center opened in 1978 at the site of the 1845 Alvarado/Castro home. A replica of their adobe home was included in the new complex. The Blume House was moved to the site. Both the Alvarado Adobe and Blume House are open to the public on Sundays. Admission is free.