There were watch manufacturers and there were case manufacturers.
American pocket watches used a system of (relatively) standard watch sizes, so it was possible for a customer to select the watch movement they wished to purchase, and then select a case to hold it.
There is a lot involved, but let’s try to make it simple.
A watch is a small timepiece intended to be carried or worn by a person.
It is designed to keep working despite the motions caused by the person's activities.
The history of the American Waltham Watch Co can be traced to the original formation of a company by three men, Howard, Davis & Dennison in 1850.
They had the then revolutionary idea of producing large quantities of Waltham pocket watches by using machinery set up to mass produce parts in order to make watches more easily affordable than they were at the time.
Watches evolved in the 17th century from spring-powered clocks, which appeared as early as the 14th century.
During most of its history the watch was a mechanical device, driven by clockwork, powered by winding a mainspring, and keeping time with an oscillating balance wheel.
Today most inexpensive and medium-priced watches, used mainly for timekeeping, have quartz movements.
Expensive collectible watches, valued more for their elaborate craftsmanship, aesthetic appeal and glamorous design than for simple timekeeping, often have traditional mechanical movements, even though they are less accurate and more expensive than electronic ones.
Some of the industrial giants of the day made their names in the watch manufacturing industry.
The companies listed below were known to have operated and produced watches in the United States in the 1800s and 1900s.