When Gibson acquired Epiphone in 1958, it moved production to its own plant in Kalamazoo, Michigan. There were a few reasons that Gibson wanted Epiphone. Epiphone had been Gibsons greatest competition before the company began to flounder. They had tooling for upright basses which Ted McCarty, (Gibson president) had long admired, and producing another brand would go some way to offer Gibson-made instruments to dealers who were not part of Gibsons existing territory agreements. Gibson have always preferred not to have too many outlets for their product.
A new building (right hand side of the above picture) was added to the Gibson plant in 1960, behind the existing Gibson plant (far left of the picture, just beyond the famous Gibson chimney). Epiphone guitars and basses were still built in this old building alongside the Gibson models, but to keep customers thinking these were different lines, the postal address used for Epiphone was the one on the far right, 47 Bush Street.
Epiphone have made, and still do make some very nice bass guitars. The company had made fine upright basses in the 1950s, but didn't make a bass guitar until Gibson took over. In 1961 it launched two models, the solid-body Newport, and the semi-acoustic Rivoli, followed by a long scale solid-body, the Embassy Deluxe, in 1963.
Production moved to Japan in 1969/70.