Great Falls residents can tour Colvin Run Mill for free on three Sundays in September as the Fairfax County Park Authority (FCPA) opens seven historic sites for guided visits marking America's 250th anniversary.

The September Sundays Free Tour Series, part of the county's Fairfax250 commemoration, launched Sunday, Sept. 13, with additional dates on Sunday, Sept. 20 and Sunday, Sept. 27. Tours are free, but space is limited and advance registration is required.

Colvin Run Mill, at 10017 Colvin Run Road, is an operational 19th-century water-powered gristmill on the National Register of Historic Places. The mill's grounds are normally free to visit, but tours and programs carry a fee, according to the FCPA's site page. The September Sundays series waives those costs.

The series covers seven sites in all. Five offer regular tours: Colvin Run Mill, Ellanor C. Lawrence Park, Green Spring Gardens, Historic Huntley and Sully Historic Site. Two buildings not typically open to the public round out the lineup, WTOP first reported.

One is the Spindle Sears House in Historic Centreville, a Sears, Roebuck & Co. kit home built in 1935. The other is the Frying Pan Spring Meeting House at Frying Pan Farm Park, a church more than 200 years old that served free and enslaved African Americans.

The meeting house has drawn attention before. Nancy Saunders, a Park Authority staff member, said during a Juneteenth tour of the building in July 2025 that the Primitive Baptist Church "…gave us the opportunity to transcribe the first 100 years, and that's why we have so much information about the enslaved members."

The Park Authority said visitors at the seven sites can experience working mills, historic homes, gardens, archaeology and farm life while learning about people whose lives connect Fairfax County to the nation's larger story.

Beyond the Sunday tours, the FCPA is also running the Fairfax250 Adventure Patch, a self-guided challenge. Participants complete six activities across three themes: learning, sharing and doing. Those who finish earn a commemorative Fairfax250 patch. Both programs are sponsored by the Fairfax County 250th Commission.

Registration for remaining September Sundays tours and details on the Adventure Patch are available on the FCPA's Fairfax250 webpage.