In America, the first and simplest truss structure was the kingpost, built around a center post with compression beams slanting downward and outward toward each shore, though its size was limited by the length of those beams. The queenpost was adapted for longer bridges, using an inverted "V" between two center posts with beams slanting downward and outward toward each shore. The Warren truss became the first major variation in bridge design by replacing the middle "V" of the queenpost with an "X," creating a much stronger design. Because kingpost, queenpost, and Warren trusses were commonly used in barns, they made an easy transition to covered bridges. In 1820, Ithiel Town patented the lattice truss system, which added strength, required shorter timbers, and used many parallel diagonal timbers running in opposite directions to support covered bridges up to 220 feet long. In 1817, Theodore Burr patented the Burr-arch truss, later helping earn him recognition as the "Father of the American Covered Bridge," by adding an arch to the vertical supports to increase bridge length and strength. In 1840, William Howe patented the Howe truss, the first system to routinely use both wood and wrought iron, with wrought iron rods as verticals and timbers as diagonal braces; after 1850 it became very popular and was strong enough for railroad use. During the 1800s, covered bridges were commonly built either by laying the full skeleton on the ground, loosely fastening it with wooden nails, then raising and joining the sections, or by hoisting each beam separately across a river, beginning with the bottom cord or cross beams and completing the truss beam by beam.