In Placentia, California, a small Native American village called Povuilamit existed. In 1857, settlers from Boston invaded the area and became part of Rancho La Zaca. In 1868 land was purchased to create a townsite, and the name “Placentia” was chosen because it means “pleasant.” The first post office opened in 1874 with John J. Hester as the first postmaster. The city’s population has grown over time due to its proximity to nearby cities such as Fullerton and Anaheim, which left much of their industrial growth in Placentia’s hands. In 1969, Interstate 5 cut off access from north-south traffic through the region. In 1980, constructing the second segment of Interstate 5 caused the Northridge earthquake to damage the already limited connection between Santa Fe Springs and Placentia. The third section completed in 1992 now carries most of the north-south traffic.

Placentia is situated at 33°50′ north latitude and 117°47′ west longitude. The elevation ranges from 12 feet at Kraemer Boulevard and Los Angeles Avenue to 132 feet on Nichols Drive, just north of Imperial Highway (State Route 39). According to the United States Census Bureau, the city has a total land area. Fullerton borders Placentia on the north and west, Brea on the south and southwest, Yorba Linda on the east, and Anaheim on the southeast.

Placentia is a city in northern Orange County. It is northeast of downtown Los Angeles. Placentia is known for its quiet neighborhoods, including detached single-family homes with some multiple-unit properties and large corporate office parks. The cities of Fullerton border Placentia on the northwest, Brea on the south and southwest, Yorba Linda on the east, and Anaheim on the southeast. It is part of the Los Angeles metropolitan area. The San Diego Freeway (I-405) runs through eastern Placentia. Other freeways and highways include:

• The Santa Ana Freeway (I-5)
• A small piece of State Route 57
• The Costa Mesa Freeway (SR/SR 55)
• The Riverside Freeway (State Route 91)

The 2010 United States Census reported that Placentia had a population of 49,041. The population density was 6,645.7 people per square mile (2,562.9/km²). The racial makeup of Placentia was 28,668 (58.5%) White (35.9% Non-Hispanic White), 1,510 (3.1%) African American, 393 (0.8%) Native American, 7,336 (15.2%) Asian, 109 (0.2%) Pacific Islander, 8,337 (17.3%) from other races, and 2,416 (4.9%) from two or more races. Hispanic or Latino of any race were 19,537 persons (40.1%). The Census reported that 48,839 people (99.4% of the population) lived in households, 313 (0.6%) lived in non-institutionalized group quarters, and 5 (0%) were institutionalized.

Some of the best grocery stores in Placentia, California, are Ralphs, Stater Bros., and Food 4 Less. Some of the best parks in Placentia are Yorba Linda Regional Park, Craig Regional Park, and Tri-City Park. Some of the best restaurants in Placentia are In-N-Out Burger, Panda Express, and Olive Garden. The average income for a household as of 2009 was $83,813. In Placentia, the population is spread out with 21.5% under 18 and 14.3% who were 65 years of age or older. Of the population 25 years and over, 83.2% had a high school degree or higher, while 33.0% had a bachelor’s degree.