Kings Mills in Deerfield Township in Warren County was originally known as Gainesboro or Gainsborough. It is believed to have been the site of the first mill in Warren County, built in the vicinity on the Little Miami River by William Wood about 1799, and remained in service until 1877. Gainesboro, with 134 lots, was laid out by Ralph W. Hunt on the west side of the river June 26, 1815. Gainesboro post office operated from Jan. 18, 1822, to August 1825. An 1856 map shows the village as Gainsborough.
In 1878, King's Great Western Powder Company was incorporated. Joseph King and his nephew Ahimaaz King, two of the founders, built a small powder mill on the Little Miami River. Gunpowder purchased from the government was refined and sold. During the first year of operation, 12,768 kegs of sporting powder and 28,067 kegs of blasting powder were produced. When Joseph King died in 1885, his son-in-law, Gershon M. Peters, became president while Ahimaaz King remained as manager. In 1887 Peters incorporated the Peters Cartridge Company. The company developed a round-table loading machine for mechanically loading shotgun shells. These were the first machine-loaded shotgun shells. Although it operated separately from King's Great Western Powder Co., there was a close relationship between the two. Originally, Peters rented space from King's before it eventually purchased some of the land and buildings. In 1889 King's Great Western Powder Co. was changed to the King Powder Company and the town of King's Mills (with an apostrophe then) was started. It was primarily a company owned town with only a few privately owned homes.
In the early 1900s, about 1,000 people were employed producing, loading and packing cartridges. The plant was a major provider of cartridges for the U. S., Great Britain, and other Allied countries. During World War I, Peters produced an average of 1.5 million cartridges a day. After the war ended in 1918, parts of the plant were closed, demolished or abandoned. In 1934, Peters Cartridge Co. was acquired by Remington Arms Company. The company revived with the start of World War II, according to George Crout in Miami Valley Vignettes. "The carbine was a short, light rifle used by many soldiers in World War II. It was issued to all Air Force personnel overseas," Crout said. "As servicemen from the Miami Valley carefully cleaned their carbines, few realized that the 30 M-1 shells they used in the 15-bullet clip were made in their own area. When the army replaced the .45 caliber sidearm with the carbine, it meant that a new caliber ammunition had to be produced in great quantities. In July, 1942 the giant Kings Mills plant was converted to the production of this new caliber of ammunition. The plant turned out more than 50 million pounds of carbine shells each month for the government. The Kings Mills Ordnance Plant was operated by the Remington Arms Company under control of the U.S. Army, and was one of America's largest cartridge plants," Crout wrote. It provided employment for many Butler Countians. Remington closed the plant in 1944. Until 1948, Columbia Records used the facility. In 1950 it was sold to Seagram's Distillery which used it for storage before selling it in 1960. Since 1972, Kings Mills has been a neighbor to the Kings Island Amusement Park on its western border. (See Coney Island for information on Kings Island.)