In 1960, US 15 from the MD 26 interchange to Harmony Grove was expanded to a divided highway. The Frederick Freeway gained exit numbers in 1965, the same year the highway's interchange with 7th Street was added. The exit numbers ranged from 1 at the freeway's interchange with MD 144 east of Frederick to 9 at the highway's interchange with MD 26; the 7th Street interchange became exit 7A. The two-lane section of the freeway was expanded to its present four-lane configuration in 1969, the same year the US 340 freeway was completed between Jefferson and Frederick. US 15's present alignment from Point of Rocks to US 340 was also under construction by 1969. When the new highway opened in 1970, US 15 was moved to the new highway and joined US 340 in a concurrency along Jefferson National Pike from Jefferson to the Frederick Freeway. The old section of US 15 from Point of Rocks to Tuscarora became a westward extension of MD 28. Buckeystown Pike from MD 28 to Washington National Pike was designated MD 85, which was extended north to MD 355 the following year. The U.S. Highway's interchange with Mt. Zion Road opened in 1972.