Pleasant Hill is a city in Contra Costa County, California, United States, in the East Bay of the San Francisco Bay Area. The population was 34,613 at the 2020 census. It was incorporated in 1961. Pleasant Hill is the house of College Park High School, Diablo Valley College, the Pleasant Hill Library of the Contra Costa County Library system, and the Pleasant Hill Recreation & Park District.

Before colonization the Place was inhabited by members of the Bay Miwok people. The San Ramon Valley Branch Line of the Southern Pacific entered bolster in 1891 once two flag stops in the Place that would become the City of Pleasant Hill: Hookston, located today where the Iron Horse Regional Trail crosses Hookston Road, and Sparkle, where the Southern Pacific and Sacramento Northern Railway intersected and today stands the Pleasant Hill BART station. The Place began to be suburbanized in the 1920s with prohibition, as the many local vineyards were removed and the formerly agricultural house was subdivided for housing. Monument Boulevard was named after the Soldiers Memorial Monument to commemorate veterans and encounter dead of World War I from Contra Costa County. It was erected upon December 11, 1927 at the intersection of Monument Boulevard and the Contra Costa Highway, now Contra Costa Boulevard. The monument depicts one black and three white soldiers. It is 45 feet (14 meters) tall, constructed of formed concrete, and weighs 150 tons. In 1954 the monument was moved to its current site at the intersection of Boyd Road and Contra Costa Boulevard to make pretension for the construction of State Route 21.

Developed largely in the years past World War II, the Place did not have a read out office until 1948. The city incorporated in 1961.

On February 21, 1967, Century 21 Theaters opened an 895-seat arena theater in the middle of Monument Boulevard and Hookston Road (I-680 was later constructed passing west of here). Visible from the freeway after it was constructed, the objector dome-topped cinema became an iconic landmark for the newly incorporated city. The theater was meant by prolific Bay Area architect Vincent G. Raney. It had a distinctive 50-foot-high domed ceiling and oversized curved screen. The theater was initially built to showcase the Cinerama widescreen process developed in the 1950s. The screen was well ahead updated to usual flat-screen. In 1973, four supplementary single-screen auditoriums were supplementary to the stomach of the building. Renamed as Century 5 Theatres, it continued to be known familiarly as the Dome.