McConnells Mill State Park, Slippery Rock Township, just over the Butler County line into Lawrence County, will be the site of "Crossing the River" about covered bridges at 2 p.m. Saturday. "Heart Hike 2" is planned at 4 p.m. Sunday. The Old Mill is open for grist mill tours at 1 and 2 p.m. Fridays, 1 and 3 p.m. Saturdays, and 2 and 4 p.m. Sundays. Corn grinding will be demonstrated from 11 a.m. to 3:30 p.m. Fridays and 11 a.m. to 5:30 p.m. Saturdays, from Memorial Day through Labor Day. Admission and parking are free. Call 724-368-9320.

Jennings Environmental Education Center, Route 528 near the intersection of Routes 8 and 173, is open from 8 a.m. to 4 p.m. weekdays and on weekends as scheduled. The trails are open daily from sunrise to sunset. Call 724-794-6011 to confirm programs.