Blackstone River Valley National Heritage Corridor and Blackstone River Valley National Historical Park are hosting a special celebration for Founders Day, the 105th birthday of the National Park Service, on Wednesday, August 25, at Old Slater Mill National Historic Landmark, 67 Roosevelt Ave., Pawtucket, RI. Festivities will run between 3 p.m. and 7 p.m. and include free guided tours of Old Slater Mill, a Plein Air Painting session, GearHeads/Junior Rangers activities, and an awards ceremony for the Volunteers-In-Parks (VIP) program.