Shipbuilding in Thomaston began as early as 1787, aided by the gently sloping banks of the St. George River, which provided access to the sea and ideal launching conditions. Early waterfront businesses stood at the mouth of Mill Creek on the east side of town, but by the 1820's shipping activity had shifted to the St. George River near Wadsworth Street, where related trades such as block-making, rigging, and chandlery clustered on Paine's Wharf. Shipbuilding made Thomaston one of the most prosperous towns of the early 1800's, and in the 1840's the industry reached its height, building 139 vessels, many of them owned and operated by local citizens. Its profits were so great that three of the seven millionaires recorded in the 1840 United States Census lived in Thomaston, having earned their fortunes as sea captains and boat builders. Among the most prominent was the Honorable Edward O'Brien, one of the country's first millionaires, whose ships were known for their broad unpainted and clear-varnished bright line; his son-in-law William Campbell added to the family's wealth through a sailmaking business in the Carr-O'Brien block, a building erected by O'Brien in 1852 at Main Street and Wadsworth Street. Wooden shipbuilding also supported many skilled trades in Thomaston, including lumber mills, blacksmiths, caulkers, spar-makers, sail lofts, hoop makers, cordage makers, painters, and carpenters. The industry declined in the following decades because of factors including the Panic of 1857, the Civil War, shortages of suitably sized local timber, the rising cost and danger of importing timber from southern forests during the fighting, and the increasing use of steam power at the turn of the century. Thomaston's last large cargo schooner, the Edna S. Hoyt, was launched in 1920, though Charles Morse then established the Morse Boatbuilding Company to build smaller vessels such as draggers, schooners, and sloops, and that tradition continued under Lyman-Morse Boatbuilding. The largest ship ever built in Thomaston was the five-masted schooner Washington B. Thomas, built by Washburn Brothers in 1903; at 289 feet and 2,689 tons, it was immense, but it ran aground at Prout's Neck in Portland just two months after launching while returning from Virginia with coal.