The first white settlement in the Richland area appeared in 1863, and by 1880 a stage coach company was established. In 1892 Nelson Rich and Howard Amon formed the Benton Water Company which brought irrigation to the area. The first post office opened in October 1905, listing the town as "Benton". A contest was held to decide the official name for the town and Richland was the winning name. (According to Robert Hitchman in Place Names of Washington (Washington Historical Society, 1985) the place was named "Richland" in 1904 after landowner Nelson Rich.) The city of Richland was officially incorporated in 1910, with a population 240.

Richland remained a small farming community until the population boomed in 1943 when the U.S. Government assumed ownership of the area and built the country's first nuclear reactor on the Hanford Site. The Manhattan District of the U.S. Army Corps of Engineers acquired the towns of Richland, Hanford, and White Bluffs, and designated the area as the Hanford Atomic Works. They began the development of the atomic bomb. In 1944, the first reactor began operation at the Hanford Project. Camp Hanford’s population peaked at 51,000, and spanned not quite two years until its abandonment in February 1945. E.I. du Pont de Nemours and company governed the city until General Electric Company, acting as administrator for the Atomic Energy Commission (later the Energy Research and Development Administration and subsequently the Department of Energy), assumed control in 1946. In 1948, the City of Richland was officially dissolved, and was reincorporated in 1958. The last production reactor closed in 1988. Today Hanford remains a research center, and the Hanford Reach remains the last free-flowing stretch of the Columbia River in the United States. Hanford was designated as a National Monument during the Clinton administration.

"... In 1883, the Northern Pacific Railroad track was being constructed from Spokane on its way to Seattle via the Yakima River and had reached a point near the Columbia River. Mr. H.S. Huson, a civil engineer with the railroad was sent to find a suitable location for a bridge across the Columbia River. They landed on a small island covered with grass and wild shrubbery known today as Clover Island. Indians called it Kin-i-wak, which meant “grassy place”. The construction crews began to arrive and set up camps along the proposed route. Huson recommended that the bridge be built at Cottonwood Landing, a short distance downriver from Kin-i-wak, but during the time of locating foundations for the bridge, he found himself calling the place Kenewick in his records and correspondence. ..." [City of Kennewick Website, 2006]

According to Robert Hitchman in Place Names of Washington (Washington Historical Society, 1985) the original name for the town was "Dell Haven", which was later replaced with the Indian name "Kennewick". The name "Kennewick" has been translated to mean "grassy place", "winter paradise", "winter heaven", and even "dried acorns".

By 1892, Nelson Rich and Howard Amon formed the Benton Land and Water Co. bringing irrigation to the area for the first time. Kennewick became an incorporated city in 1904. Thousands of people moved into the town with the advent of World War II, the Hanford Atomic Project in nearby Richland, the construction of McNary Dam, and the Columbia Basin Irrigation Project.