Mass production of clocks with interchangeable parts began in the United States after the American Revolution (1775-1783). In Connecticut's Naugatuck River Valley, clock makers, brass workers and machinists made important strides toward increasing clock production. In the first half of the 19th century, they invented and produced clocks average citizens could afford. Arguably, the greatest of these entrepreneurs, Eli Terry, developed mass-production and interchangeable-part technology to economically produce a form of "box clock" which required winding only once a day. Amazingly, Terry's famous "Pillar and Scroll Mantle Clock" sold over 6000 models in 1817, the first year of its production. The $15 to $20 priced timekeeper housed in an elegant case was instrumental in sprouting competing clock models and makers not only in Connecticut but worldwide. About the same time in Plymouth Hollow (now Thomaston), Connecticut, Seth Thomas founded the Seth Thomas Clock Company, which was, by the mid-20th century, one of the largest clock factories in the world.

Starting in about 1830, Connecticut clockmakers used stamped brass gears for their clocks to produce new clocks with the same interchangeable parts approach as the wooden clock industry had developed. Companies like the Jerome Manufacturing Company of Derby, CT turned out 130,000 clocks a year in brass by the early 1850’s, helping to make the United States the leading clock-making country of the world. Cheap clocks were affordable to almost anyone by that period.

Watches were not produced in significant volume in the United States until about 1800, when Thomas Harland of Norwich, Connecticut, established a factory with a capacity of 200 units a year. In 1836 the Pitkin brothers of East Hartford, Connecticut, produced the first American-designed watch and the first containing a machine-made part. Despite a reputation for accuracy and durability, the manufacture of this watch was discontinued as a result of the depression of 1837, which temporarily crippled American industry.

Watches also became cheaper as production rose. American horologists Aaron Dennison and Edward Howard, working in Massachusetts, invented and perfected automatic production machinery in the 1850s. In 1854, the Waltham Watch Company of Waltham, Massachusetts, was established by Aaron Dennison. The company went on to make the first watches with interchangeable parts and the first 100% American-made watch. The advanced machinery designed at the Waltham Watch Company spread to other industries.