Complex sentence: Duquesne was home to the largest blast furnace in the world named the "Dorothy Six" until its abandonment; the city's population peaked in 1930, and deindustrialized beginning in the 1960s.
Split into simpler sentences: Duquesne was home to the largest blast furnace in the world, named the "Dorothy Six". The city's population peaked in 1930, then declined with deindustrialization beginning in the 1960s.