The northern segment was extended south to Morgan Run and the southern segment north to Gillis Road in 1928. Ridge Road was completed from Mount Airy to Westminster when the gap through Taylorsville was filled in 1929. The Germantown–Mount Airy portion of Ridge Road once served as the primary highway between Frederick and Rockville, but was eclipsed by the  highway through Hyattstown and Urbana when that highway, designated US 240 (now MD 355), was completed in 1926.
The changes made to Ridge Road involved extending its northern part south to Morgan Run and its southern part north to Gillis Road in 1928. Ridge Road was then finished from Mount Airy to Westminster after the gap through Taylorsville was closed in 1929. The Germantown–Mount Airy section of Ridge Road had previously served as the main route between Frederick and Rockville, but was later surpassed by the highway through Hyattstown and Urbana when US 240 (now MD 355) was completed in 1926.