Complex sentence: Initially, the plant was known as the Twin Cities Ordnance Plant but it was renamed the Twin Cities Arsenal in 1946 and finally, in 1963, the Twin Cities Army Ammunition Plant (TCAAP).
Split into simpler sentences: Initially, the plant was known as the Twin Cities Ordnance Plant. It was renamed the Twin Cities Arsenal in 1946 and finally, in 1963, the Twin Cities Army Ammunition Plant (TCAAP).