Complex sentence: Most European immigrants settled in the cities, as well as in the many small towns that were founded along the expanding railway system, though from the 1930s, rural migration into the nation's larger cities accounted for much of their population growth.
Split into simpler sentences: Most European immigrants settled in the cities, and the many small towns founded along the expanding railway system. From the 1930s rural migration into the nation's larger cities accounted for much of their population growth.