The Midwest was highly developed with new transportation. The Spanish controlled the territory of Texas. Americans gained strength to settle after the Texas Rebellion won independence. Texas was still in the debate over being a slave state because English settlers had brought slaves into an abolished state. The Mexican-American War brought back slavery, which put more slaves in the Senate. A compromise was reached that made California a free state and Texas a slave state. Ulysses S. Grant felt the Mexican-American War would lead to Civil War.