During their heyday in the mid- to late 1800s, more than 150 covered bridges dotted the landscape of Connecticut and Rhode Island. Since that time, floods, fires, and progress have claimed all but three of the historic structures. Covered bridges were heavily concentrated in the hills of northwestern Connecticut, spanning the Farmington, Housatonic, and Naugatuck Rivers. In Rhode Island, most were built by the railroads in Woonsocket, Providence, and other communities in the northern part of the state, though few pictures are known to exist. Connecticut was the birthplace of two of the nation's best known covered bridge designers: Ithiel Town and Theodore Burr. Half of the covered bridges currently standing in the United States are supported by trusses patented by Town or Burr.