Which state has the most covered bridges in the US?

Pennsylvania has the most with about 200.

http://pacoveredbridges.com/

Extensive information on the exact locations and numbers of these bridges was found at woodcenter.org/CoveredBridges/queryMain.cfm#panel1-4 (webpage no longer exists). The interactive map there showed Pennsylvania was first at 211 existing covered bridges, followed by Ohio (133) and Vermont (95). The "lost bridges" version of that map at woodcenter.org/CoveredBridges/queryMain.cfm#panel1-5 (webpage no longer exists) showed that Ohio once had the most, with 3174 now lost, compared to 1657 in Pennsylvania.

At one time, the United States had as many as 12,000 covered bridges, according to the book "Covered Bridges Today." Estimates on the current number range from roughly 850 to about 1,000. Pennsylvania, with 219 covered bridges, about 150 of which still are in use, has the most. “The preservation efforts are rather spotty,” says Roger Small, corresponding secretary of the Theodore Burr Covered Bridge Society of Pennsylvania. "It depends on the political and local climate."

https://www.americancityandcounty.com/1998/03/01/americas-covered-bridges-spanning-the-years