The Sunday River Bridge is also known as the Artist's Covered Bridge. It is the most photographed and painted of Maine's nine remaining historic covered bridges. The 87-foot Paddleford Truss bridge is no longer in use and is easily accessed from the road. You can walk across the old bridge.
If you go:
There is a pullout just before the bridge with room for a few cars. There is a place just down from there to take photos of the bridge. Use caution walking along the banks or if crossing the replacement bridge.
Links:

Sunday River Bridge
Sunday River
Newry, Maine 04261 USA
communications@mainedot@maine.gov
Mailing address:
Maine Department of Transportation
16 Statehouse Station
Augusta, ME 04333 USA
Phone Numbers:
Maine DOT
+1 (207) 624-3000
+1 (207) 624-3000