Early on, the area that is now Seal Beach was known as “Anaheim Landing”, as the boat landing and seaside recreation area named after the nearby town of Anaheim. The site of Anaheim Landing is now registered as a California Historical Landmark.
By the 20th century, it was known as Bay City, but there was already a Bay City located in Northern California. When the time of incorporation on October 27, 1915, the town was named Seal Beach. The town became a popular recreation destination in the area. The Joy Zone, a beach-side amusement park built in 1916, was the first in Orange County.
The United States Navy’s Naval Weapons Station Seal Beach was originally constructed during World War II for loading, unloading, and storing of ammunition for the Pacific Fleet, and especially those US Navy warships home-ported in Long Beach and San Diego, California. With closure of the Concord Naval Weapons Station in Northern California, it has become the primary source of munitions for a majority of the U.S. Pacific Fleet.

Seal Beach is located at WikiMiniAtlas33°45′33″N 118°4′57″W (33.759283, -118.082396).
According to the United States Census Bureau, the city has a total area of 13.0 square miles (34 km2). 11.3 square miles (29 km2) of it is land and 1.8 square miles (4.7 km2) of it (13.45%) is water.

The 2010 United States Census reported that Seal Beach had a population of 24,168. The population density was 1,853.3 people per square mile (715.6/km2). The racial makeup of Seal Beach was 20,154 (83.4%) White (76.9% Non-Hispanic White), 279 (1.2%) African American, 65 (0.3%) Native American, 2,309 (9.6%) Asian, 58 (0.2%) Pacific Islander, 453 (1.9%) from other races, and 850 (3.5%) from two or more races. Hispanic or Latino of any race were 2,331 persons (9.6%).
The Census reported that 23,943 people (99.1% of the population) lived in households, 22 (0.1%) lived in non-institutionalized group quarters, and 203 (0.8%) were institutionalized.

There were 13,017 households, out of which 1,866 (14.3%) had children under the age of 18 living in them, 4,891 (37.6%) were opposite-sex married couples living together, 788 (6.1%) had a female householder with no husband present, 283 (2.2%) had a male householder with no wife present. There were 383 (2.9%) unmarried opposite-sex partnerships, and 66 (0.5%) same-sex married couples or partnerships. Of the households, 6,312 (48.5%) were made up of individuals and 4,340 (33.3%) had someone living alone who was 65 years of age or older. The average household size was 1.84. There were 5,962 families (45.8% of all households); the average family size was 2.65.

The population was spread out with 3,151 people (13.0%) under the age of 18, 1,176 people (4.9%) aged 18 to 24, 4,076 people (16.9%) aged 25 to 44, 6,513 people (26.9%) aged 45 to 64, and 9,252 people (38.3%) who were 65 years of age or older. The median age was 57.3 years. For every 100 females there were 78.8 males. For every 100 females age 18 and over, there were 76.3 males.
There were 14,558 housing units at an average density of 1,116.4 per square mile (431.0/km2), of which 9,713 (74.6%) were owner-occupied, and 3,304 (25.4%) were occupied by renters. The homeowner vacancy rate was 2.0%; the rental vacancy rate was 4.4%. 17,689 people (73.2% of the population) lived in owner-occupied housing units and 6,254 people (25.9%) lived in rental housing units.
During 2009–2013, Seal Beach had a median household income of $51,242, with 9.9% of the population living below the federal poverty line.

The major employer in Seal Beach is The Boeing Company, employing roughly 1,000 people. Its facility was originally built to manufacture the second stage of the Saturn V rocket for NASA’s Apollo manned space flight missions to the Moon and for the Skylab program. Boeing Homeland Security & Services (airport security, etc.) is based in Seal Beach and Boeing Space & Intelligence Systems (satellite systems and classified programs) is headquartered in Seal Beach.