Prior to the visit of explorer Cabrillo, the area now known as the Oxnard Plain was inhabited by Chumash Indians. When Cabrillo reported to the Queen of Spain in 1542, he described the area as the "Land of everlasting summers." There were approximately 50,000 Indians in the vicinity at the time.  Early Spanish settlers enjoyed the benefits of the lush, fertile soil and spoke of "mustard stalks higher than a vaquero's horse."

Then other European immigrants began to settle in the area and farming became a major industry.  Lima beans made up the primary crop but then Albert Maulhardt invited Henry T. Oxnard, who was in the sugar cane and beet sugar business, to visit. Mr. Oxnard agreed that sugar beets would grow well on the fertile plain.  He agreed to teach the farmers how to raise the crop successfully and the Oxnard Brothers built a factory in the middle of the fields to process the beets.  Land for the factory was purchased from Thomas A. Rice.  A town quickly sprang up near the factory to meet the needs of the construction workers and their families.  The Oxnard Improvement Company was created in 1898 to design the town site which was laid out, European style, around a town square (now Plaza Park).  The land for the town was purchased from J. G. Hill.  The factory began operation in 1899, with Major J. A. Driffill as the plant manager.

The first church was built in 1900 and the Ventura County Railway was built to transport beets from the fields.  The Oxnard Union High School District was formed in 1902, and the city incorporated June 30, 1903. In 1906, educator and first mayor of Oxnard, Richard B. Haydock applied for assistance from the Andrew Carnegie Foundation to construct a library building.

Early business included the Bank of A. Levy, Lehmann Brothers Department Store, Poggi's Drug Store and a large hotel.  The factory operated for 60 years but closed its doors in 1958 because vegetables had replaced sugar beets as the primary local field crop.

During the 1930's those interested in commercial water shipping took advantage of the deep channel extending out from Port Hueneme Harbor.  The Oxnard Harbor District was formed in 1938 and built a commercial and yacht harbor.  Canneries came to the port and steamship companies lined up for regular coastwise service.

Oxnard experienced its greatest growth during World War II.  The U.S. Naval Construction Battalion Center was established at the harbor and the first U.S. Naval Air Missile Test Center was constructed at Point Mugu in 1946. Former Oxnard Mayor, Edwin Carty, was a major real estate developer during the 1940s and '50s and Oxnard Air Force Base was established in 1952.  Martin V. Smith began building restaurants and motels in the 1940s and his Colonial House on Oxnard Boulevard attracted the Hollywood crowd during the 1950s.  Smith later built the two tall buildings rising up out of the Oxnard Plain in the area known as Financial Plaza.

Oxnard is now the largest city in Ventura County and is the center of the vast alluvial plain, now known as the Oxnard Plain, 180 square miles of some of the richest agricultural land in the State of California.