Aeronca Champ pilot reported engine failure inflight. Pilot made an off airport landing.

Narrative

At XA00 departed ZZZ; home base and grass strip. Clear weather and light winds all day. Destination ZZZ1 12 nm; non-tower; to pick up another pilot. Departed ZZZ1 at XA30 to fly to ZZZ2 33nm; non-tower; for fly-in. Departed ZZZ2 at XC45 to return to ZZZ1. During cruise at 2;100 engine began running ruff; power was cutting in and out. Check fuel valve on; only 1 fuel tank. Closest airport was 5 miles and had high power lines between us. Made a off airport landing in Location A. No damage to aircraft or Location A. Aircraft is a 1945 taildragger. Engine still has power; taxied to Person A standing in Location A. Shut engine down; opened cowl checked engine spark plugs wires; air filter and cables. Used dip stick to check fuel showed just under 4 gallons; capacity is 13 gallons. Person A drove me to [nearest] airport with 5 gallon gas can. Bought 5 gallons and return to aircraft to add more fuel. Engine run-up and full power check normal. Departed Location A solo and returned to ZZZ. No engine roughness. Lessons learned: Keep the fuel tank always above 5 gallons; there is no published unusable fuel in 1945. Check fuel quantity visually before every departure.