My mom started with Peat Marwick and Main, when they were that. She was a specialist in multi-state returns.
I think Main Herdman merged with Peat happened in 1979. I was with E&E at the time. It was the first of the “Big 8” mergers.
E&E then became Ernst & Whinney (1979 or 1980) due to an international merger. We joked that the E&W stood for “evenings and weekends” as we worked long hours. In 1989, Ernst & Whinney and Arthur Young merged to form Ernst & Young.