El Centro ("The Center" in Spanish, formerly, Cabarker) is the county seat of Imperial County, California, United States and the largest city in the Imperial Valley, the region east of San Diego. It is also the largest U.S. city to lie entirely below sea level (- 50 feet). El Centro is Spanish, and means the center. This name is fitting, because it is the core urban area and principal city of the 'El Centro, California Metropolitan Statistical Area' which encompasses all of Imperial County. It is home to retail, transportation, wholesale, and agricultural industries.The city's population was 37,835 at the 2000 census. The 2006 population is 40,563.
According to the United States Census Bureau, the city has a total area of 9.6 square miles, (24.9 km²), of which 9.6 square miles, (24.8 km²), of it is land and 0.04 square miles, (0.1 km²), of it is water.
El Centro is located in the Imperial Valley(considered locally as synonymous with Imperial County). The city is 50 feet below sea level and the largest city in the United States below sea level. The Imperial Valley is in the Colorado Desert, an extension of the larger Sonoran Desert.
In this region, the geology is dominated by the transition of the tectonic plate boundary from rift to fault. The southernmost strands of the San Andreas Fault connect the northern-most extensions of the East Pacific Rise. Consequently, the region is subject to earthquakes, and the crust is being stretched, resulting in a sinking of the terrain over time.
Spanish explorer Melchior Díaz was one of the first Europeans to visit the area around El Centro and Imperial Valley in 1540. The explorer Juan Bautista de Anza also explored the area in 1776 (an elementary school in El Centro now bears his name). Years later, after the Mexican-American War, the northern half of the valley was annexed by the U.S., while the southern half remained under Mexican rule. Small scale settlement in natural acquifer areas occurred in the early 1800s (the present-day site of Mexicali), but most permanent settlement (Anglo Americans in the U.S. side, Mexicans in the other side) was after 1900.
Originally part of San Diego County, the Imperial Valley was settled by farmers once water from the Colorado River was diverted via canals to irrigate the desert valley floor.
By 1907 Imperial County was incorporated into California and by then much of the valley was successfully irrigated.
The City of El Centro was incorporated on April 16, 1908. By 1910, the population of the city had reached 1,610. By 1920 it was 5,646. One reason for this rapid growth was El Centro's becoming the county seat of Imperial Valley.
By the mid-1940s, El Centro had become the second largest city in the Imperial Valley, with a population of about 11,000 people. El Centro had also become the location of the Imperial Irrigation District (IID) administrative offices.Agriculture has been an important industry within El Centro since the 1940s, because of its strategic location near rail lines and Highway 80 and 99 - more than 35 growers and shippers still operate in El Centro. However, by the early 1980s the two largest employment sectors in El Centro were Government and Wholesale/Retail Trade, reflecting El Centro's emerging role as a regional administrative and commercial center.