The original settlement of Waterbury was in 1674 in the Town Plot section. King Philip's War caused it to be vacated and the location was changed to the Western part of the Green in 1677. Both sites are marked.   The Algonquin name for the area was "Matetacoke" meaning "place without trees." It appeared as "Mattatock" in 1673, and "Mattatuck" in the General Court record of May 18, 1674.

The name changed to Waterbury on May 15, 1686, when the settlement was admitted as the 28th  town in the Connecticut colony.  It then included all parts all or parts of the later town of Watertown, Plymouth, Wolcott, Prospect, Naugatuck, Thomaston and Middlebury.  The name Waterbury was chosen because of all the streams flowing into the Naugatuck.  Waterbury was incorporated as a city in 1853.

Waterbury occupies 28.9 square miles.  Its elevation is between 215 and 965 feet above sea level.