MD 185's history can be divided into two segments. The portion south of Kensington was included in the state highway system by 1927 as an extension of Connecticut Avenue out of the District of Columbia and was the westernmost stretch of MD 193. The Chevy Chase to Kensington stretch was expanded to a divided highway in the 1950s. The segment of MD 185 between Kensington and Aspen Hill was built as a divided highway on a new alignment in the 1960s and designated MD 185. The MD 185 designation was extended south of Kensington, replacing MD 193, in the 1970s. Construction projects in the 1980s and early 1990s completed MD 185 as a six-lane highway.