Frederick Freeway (US 40), onto which US 15 exits. The ramps from westbound US 340 provide full access to I-70, I-270, US 15, and US 40. The roadway continues northeast as Jefferson Street, which reduces to a two-lane undivided street that heads toward an intersection with MD 144 (South Street eastbound and Patrick Street westbound) just west of downtown Frederick. The portion of Jefferson Street between the overpass of US 40 and just west of Jefferson Street's intersection with Pearl Street is unsigned US 15B. History In Maryland, US 340 follows the corridor of the old road from Frederick to Harpers Ferry, part of which was organized as the Frederick and Jefferson Turnpike between the two towns. This highway became one of the original state roads marked for improvement by the Maryland State Roads Commission in 1909. The commission purchased the right-of-way of the turnpike in 1911 and resurfaced the Frederick–Jefferson highway with a wide macadam surface in 1915. The segments from Jefferson to Petersville and from Petersville to Knoxville were placed under construction in 1911 and completed as a macadam road in 1912. The highway from Knoxville to the Potomac River opposite Harpers Ferry was completed as a concrete road in 1919. The Frederick–Knoxville highway was widened to in width around 1926 and became part of US 340 in 1927. US 340 was widened again, this time to between Frederick and Knoxville, by 1934. US 340 was widened and resurfaced with bituminous concrete from Knoxville to the approach to new bridge at Sandy Hook in 1948. In conjunction with the construction of the Frederick Freeway, US 340's cloverleaf interchange with US 40 was built in 1954 and 1955. Jefferson Street in Frederick was widened in 1956. When US 40 was moved from Patrick Street to the Frederick Freeway in 1959, US 340's eastern terminus was moved from Patrick Street west to the new interchange. Construction on the US 340 freeway began when the highway's bridge across Catoctin Creek was built in 1961. This bridge came into use in 1964 when the freeway segment between the MD 180 interchange east of Petersville and the ramp from MD 180 west of Jefferson was opened, replacing the curvaceous old alignment at Catoctin Creek. The present alignment of US 340 opened as a four-lane divided highway from the Valley Road / Keep Tryst Road intersection in Sandy Hook east to Weverton also opened