Complex sentence: Mohawk saw its golden age in the late 1950s and early 1960s, acquiring the Convair 440 in 1958, to which Martin 4-0-4s were added in 1960.
Split into simpler sentences: Mohawk saw its golden age in the late 1950s and early 1960s. In 1958 it acquired the Convair 440, to which Martin 4-0-4s were added in 1960.