Rose Valley is a small, historic borough in Delaware County, Pennsylvania, United States. Its area is 0.73 square miles, and the population was 913 at the 2010 census. The area 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 of land around the former Rose Valley textile mill. Price was a follower of Henry George's economics. Price also co-founded Arden, Delaware, a utopian single tax community based on Henry George's economic model. Nevertheless, the Georgist single-tax ideal was never implemented in Rose Valley. Crafts works soon foundered, leaving a legacy of impressive architecture, a preserved landscape, and a regional theatre, the Hedgerow Theatre, 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.