Rose Valley is a small, historic borough in Delaware County, Pennsylvania, United States. Its area is 0.7 square miles (1.8 km2) and the population was 944 at the 2000 census. It was settled by Quaker farmers in 1682, and later water mills along Ridley Creek drove manufacturing in the nineteenth century. In 1901 Rose Valley was founded as an Arts and Crafts community by architect Will Price, who bought 80 acres (320,000 m2) of land around the former Rose Valley textile mill. Price, a follower of the Henry George's economics was also a co-founder of Arden, Delaware, where he tried to create a single-tax utopian community. Nevertheless the single-tax ideal was never implemented in Rose Valley and crafts works soon foundered, leaving a legacy of impressive architecture, a preserved landscape, and a regional theatre, the Hedgerow Theatre (founded in 1923), as well as an artistic community that includes writers, painters, and architects. As a former mayor said, "Rose Valley is an island of non-conformity." The Rose Valley Historic District, covering essentially all of the borough, was listed on the National Register of Historic Places in 2010.