DE 261 was originally designated along Foulk Road in the 1930s. In the 1960s, most of the route was widened into a four-lane road. The southern terminus at US 202 was reconstructed into an interchange in the 2000s. PA 261 was first designated in 1928 along Foulk Road between the Delaware border and PA 61 and PA 161 in Chelsea. The route was extended north along Valley Brook Road to US 1 in Chester Heights by 1940. The northern terminus of PA 261 was moved to its current location by 1980.