There are a little over 100 authentic covered bridges in the state of Vermont, giving the state the highest number of covered bridges per square mile in the United States. A covered bridge is considered authentic not due to its age, but by its construction. An authentic bridge is constructed using trusses rather than other methods such as stringers (a popular choice for non-authentic covered bridges).
Many of the covered bridges are on the National Register of Historic Places. Some are still in use on roads, while others have been retired but can still be visited.