Originally an agricultural community in the early 20th century, Montebello was known for its prolific production of flowers, berries, fruits, and vegetables. The first flower show was sponsored by the Montebello Woman’s Club and held in the Montebello High School auditorium on Whittier Boulevard in 1912. The Montebello – El Carmel (South Montebello) Improvement Association, the predecessor of the Montebello Chamber of Commerce, operated from September 1907 to April 1912. Its purpose was “to improve and beautify the community.” Some of its achievements were: Whittier Boulevard was paved, trees planted along the streets, laid the groundwork and established the first high school, strived to have the name of Newmark dropped and to have the entire area incorporated as the City of Montebello. On October 19, 1920, the city's name was officially changed to Montebello and it was incorporated as the 35th of the present cities in Los Angeles County, and the official seal contained a red poinsettia in the center.

On June 29, 1922, the Board of Supervisors of the County of Los Angeles received a petition for the organization of the South Montebello Irrigation District brought before by petitioners, being a majority in the number of the holders of title to lands in the herein proposed Irrigation District. 

On October9, 1922, the Board of Supervisors re-affirmed its conclusions by resolution, defined the bounderies of the proposed District, divided the District into three divisions and called for an election to be held on November 14, 1922, and made an order decalring that the said South Montebello Irrigation District was duly organized and that the following Directors were duly elected: Director for the First Division, John H. Dutcher; Director for the Second Division, Edward P. Haskell, Director for the Third Division, JamesP. Dilyea.

On December 05, 1922, New Secretary, Sarah F. Becker was instructed to write to Carmel Water Company requesting a sale price for 7 ½acres on Bluff Road and all rights of way owned by Carmel Water Company. The first resolution of the new South Montebello Irrigation District is passed authorizing a bond of $125,000 to purchase the Carmel Water Company and begin serving water to the El Carmel Tract.