The Seth Thomas Clock Company was organized as a corporation on May 3, 1853 in Plymouth Hollow, Connecticut (later to become Thomaston) to succeed the earlier clock-making operation of the founder. Seth Thomas (1785-1859) had been manufacturing clocks at the site since 1814.
After the founder's death in 1859, his son Aaron became president and began to add new clocks to the company's line. About 1862, the firm purchased the patent rights of Wait T. Huntington and Harvey Platts of Ithaca, New York and added a perpetual calendar clock to their line. They also added a line of tall-case clocks in the 1880’s
The Seth Thomas Clock Company was very prosperous into the 20th century and was considered to be one of the premiere American clock manufactures, even by their competitors. Between 1865 and 1879 they operated a subsidiary firm known as Seth Thomas' Sons & Company that manufactured a higher-grade 15-day mantel clock movement and during that period were major supporters of a New York sales outlet known as the American Clock Company. After 1872 they also became a major manufacturer of tower and street clocks.
Between 1884 and 1915 Seth Thomas manufactured a line of jeweled pocket watches. Most of the tooling for the watch factory was built using the production facilities of the Seth Thomas clock factory. The first watch to reach market was an 18-size, stem-wind, 3/4 plate model in 1885. Their early watches were 11-jewel and 16,000 beat train. By 1886, production had started on four additional grades of quick-train (18,000 beat per hour) watches: a 7J, 11J, 15J and 17J model. Production of watches ceased in 1915.
On January 1, 1931, the firm became a subsidiary of General Time Instruments Corporation and soon passed from family control. The firm's decline was gradual over the next 50 years and culminated in the firm's move from Connecticut to Norcross, Georgia in 1982. The Colibri group of Providence, RI currently owns the Seth Thomas trademark and the Seth Thomas name is once again appearing on clocks.
Adapted from http://www.pocketwatchrepair.com/histories/seththomas.html