Arnold incorporated in 1957 from portions of Meramec Township, growing through the 1960s and 1970s as Jefferson County suburbanized from the north. The city's position at the confluence of the Meramec River and the Highway 55/141 corridor made it a natural commercial hub for the county's northern population, and the commercial strip along 141 remains the most significant retail concentration in the northern county.

The Meramec River corridor defines Arnold's eastern boundary and provides the flood-prone bottomland that has shaped the city's development pattern — residential development concentrated on the higher terrain west of the bluffs, with the river corridor providing recreational access, wildlife habitat, and the seasonal flooding that affects properties near the water. Arnold's position on the Meramec places it within the same flood dynamics that affect communities throughout the Meramec watershed from Eureka through Jefferson County.

Jefferson County Pest Profile

Arnold's combination of Meramec River adjacency, established 1960s–1970s housing stock, and the wooded ravines of Jefferson County's rolling terrain creates a full-spectrum pest pressure profile. Termite activity is significant in the older housing stock, particularly in the neighborhoods with crawlspace construction and the tree-to-structure wood contact that mature landscape installations produce over decades. The river corridor creates seasonal mosquito pressure and supports the wildlife populations — deer, raccoon, opossum — that create secondary pest pressure in adjacent neighborhoods. D&D Pest Control serves Jefferson County — visit ddpestcontrolmo.com.