Colvin Run Mill, the Park Authority site, is a finalist in a web-based contest sponsored by the National Trust for Historic Preservation and American Express.

The site with the greatest number of votes will receive $100,000 in preservation prize money. To vote, go daily to www.PartnersinPreservation.com.

and vote daily.

Sharing photos, video and the link via Facebook, Twitter, Instagram and FourSquare adds more votes for the mill.

Polls are open through May 10.

Login, link up and vote for Colvin Run Mill.

What your votes will accomplish: For the past four decades, only the basement and first floor of the Fairfax County mill have been open to the public. Colvin Run Mill would use the prize money to fully restore the second and third levels, complete with functioning equipment to dry and sift flour and meal the old-fashioned way. Then visitors can see how the mill works from top to bottom.