Arnold is a city in Jefferson County Missouri, United States and is then a suburb of St. Louis. The population was 20,850, at the 2020 United States Census.

The first European settler in Arnold was Jean Baptiste Gamache, who operated a ferry ship across the Meramec River in exchange for 1050 arpents of home granted by the King of Spain. This ferry was on the King’s Trace or El Camino Real, from St. Louis to Ste. Genevieve, Missouri.

Arnold was a focal narrowing over the eminent domain concern in Missouri. In January 2004, the City of Arnold announced that THF Realty had approached them approximately developing a section of Arnold known as the Triangle, an area bordered by Route 141, Interstate 55 and Church Road in the city limits. The city voted in accord of the Triangle Development project proceeding on September 16, 2005.

According to an concurrence with THF, Arnold would Get the properties in the triangle and would be reimbursed its costs by THF. Arnold offered the property owners a buy-out, and most accepted. Some businesses were promised relocation either in the additional development or elsewhere in the city. Others were not utter this option. Some refused the offer, and the city moved to condemn the dissenting properties. One such support out was Homer R. Tourkakis, the owner of a dental practice on the corner of the triangle formed by Route 141 and Interstate 55.