Answer:
Cotton, Cattle, and Railroads = Texans grow crops and raise livestock in the late 1800s.
Age of Oil and Progressive Era = Texans discover oil at Spindletop field in 1901.
Great Depression and WWII = Texans struggle to survive in the Dust Bowl in the 1930s.
Civil Rights and Conservatism = Texans fight for social justice in the 1950s and 1960s.