U.S. Route 209

U.S. Route 209 (US 209) is a 211.74-mile (340.76 km) long U.S. Highway in the states of Pennsylvania and New York. Although the route is a spur of US 9, US 209 never intersects US 9, making the connection via US 9W instead. The southern terminus of the route is at Pennsylvania Route 147 (PA 147) in Millersburg, Pennsylvania. The northern terminus is at US 9W north of Kingston in Ulster, New York, where the road continues east as New York State Route 199 (NY 199). US 209 is one of the original highways in the 1926 U.S. Highway System plan. In Pennsylvania, the highway travels through the length of the Delaware Water Gap National Recreation Area. For part of its route in New York, US 209 runs alongside the defunct Delaware and Hudson Canal, which ran from Port Jervis to Kingston.

US 209 was assigned as part of the establishment of the U.S. Highway System in 1926. The route was initially an intrastate highway contained entirely within the state of Pennsylvania. It began at an intersection with US 11 (now US 22 / US 322) in Clarks Ferry (east of Duncannon) and ended at U.S. Route 6 in Milford. US 209 was extended northward to US 9W in Kingston, New York, c. 1935 and truncated to Millersburg, Pennsylvania, by 1938. The portion of US 209 in New York north of Port Jervis was previously designated as US 6 from 1926 to 1928 and U.S. Route 6N from 1928 to 1933.

US 209 was realigned onto limited-access highways in two locations along its routing during the 1960s. In Kingston, New York, construction began on a highway bypassing downtown to the northwest in the early 1960s. The highway began at US 209 south of the city and ended at US 9W north of downtown Kingston. It opened to traffic as a realignment of US 209 by 1964. In Stroudsburg, Pennsylvania, US 209 was moved onto a pair of new expressways south and east of the borough in the 1960s. US 209's former routing into Stroudsburg was redesignated as US 209 Business.