On October 7, 1896, a group of investors formed a clock company at Kittery, ME called the Boston Clock Company in order to succeed the defunct firm of the same name. The following October 29th, at the time of the foreclosure of Joseph H. Eastman's Eastman Clock Company, one of the principals of the new Boston Clock Company purchased at public auction the newly built factory and boiler of the defunct Eastman Clock Company for $6,300.

A new firm known as the Chelsea Clock Company was formed and on August 4, 1907, the Eastman factory was transferred to the new firm by the new Boston Clock Company. Though this second Boston Clock Company was merely a firm on paper and never commenced manufacturing under that name, the Chelsea Clock Company revived the Boston Clock Company name in 1909 and used it on a line of clocks with lesser grade movements until about the time of the Great Depression. In the 1970's, Chelsea again revived the Boston name for use with a cheaper line utilizing foreign movements.

The Chelsea Clock Company has enjoyed a long, successful business primarily manufacturing superior quality clocks. They were particularly known for their good quality Willard‑style banjo clocks and other wall clocks manufactured prior to 1930 and more especially for their marine clocks which they continue to manufacture to the present. By 1975, the firm employed 80.

In the latter part of 1969 the Chelsea Clock Company was sold to Automation Industries of Los Angeles, CA, which took over the firm January 2, 1970, and worked under that firm's Kenyon Marine Division of Guilford, CT. In 1972, the firm was taken over by Bunker‑Remo of Illinois.

Chelsea remains in business to the present, though perhaps not as financially healthy as in the past. The retail prices of their clocks have skyrocketed in the last decade, some models retailing for more than $ 1,000. In the 1980's, a disastrous fire caused by an irresponsible neighboring firm destroyed the firm's warehouse and some of the firm's records and most of its repair parts, some dating back to the firm's early years. Prior to this time the firm could supply replacement parts for most of its earlier models.