Seneca evolved from a community centered on commerce into a long-used recreation area where Seneca Creek meets the Potomac River. Until the early 20th century, the C&O Canal and the Seneca Sandstone Quarry and Cutting Mill provided work for local residents and newly arriving immigrants, but after those enterprises closed, their former industrial spaces were adapted for leisure, with the quarry used for picnics and the cutting mill race becoming a popular bathing place. By the start of World War I, summer cottages lined Riley’s Lock Road, and visitors enjoyed fishing, birdwatching, boating, and stays at Hotel Seneca, which operated until the 1970s. Over time, Seneca became one of the last places along the Potomac River with public access, drawing heavy weekend recreation and filling accommodations at Seneca Creek State Park after it opened in 1958. After Hurricane Agnes in 1972, M-NCPPC bought half of the flood-damaged homes to create additional parkland beside state and federal holdings, and today the 20-acre park includes an accessible canoe and kayak launch and a boat ramp.