Wittnauer was originally Longines' agent (importer) in the US, and they became, in a roundabout way, Longines' sister branch for the North American market. However, despite what I've read in other places, I don't believe Wittnauer ever owned or merged officially with Longines. They were two separate companies.
Most Longines watches sold in the US during the 1950s-1970s started as movements (and other components) imported from Switzerland, and then they were cased and timed in the US by Wittnauer. To my knowledge, Wittnauer didn't manufacture their own cases, but farmed that out to other American watch case manufactures. Wittnauer also used unique model and collection names for Longines watches, that were different from the catalogues for Longines in Europe. There are likely many models that were unique to the US market as they were being assembled by Wittnauer.
