The history of the city goes back to 897. After becoming the meeting point of two railroads in 1862, development of industry in Wetzlar took a major leap forward. Wetzlar in particular became known for its optical industries: cameras and other photographics equipment from Leitz (now Leica), binoculars from Hensoldt, and microscopes from Leitz, Buderus and Seibert.
In 1977 Wetzlar was merged with the neighboring city Gießen to form the new city Lahn, however this attempt to reorganize the administration was very unpopular and was reverted in 1979.