Between 1861 and 1877, the United States completed its conquest of the continent. After the Civil War, expansion of railroads fostered integration of the national economy. Republican policymakers promoted this integration through protective tariffs, while federal court rulings facilitated economic growth and strengthened corporations. To attract foreign investment, Congress placed the nation on the gold standard. Federal officials also pursued a vigorous foreign policy, acquiring Alaska and asserting U.S. power indirectly through control of international trade in Latin America and Asia.

An important result of economic integration was incorporation of the Great Plains. Cattlemen built an industry linked to the integrated economy, in the process nearly driving the native bison to extinction. Homesteaders confronted harsh environmental conditions as they converted the grasslands for agriculture. Republicans championed homesteader families as representatives of domesticity, an ideal opposed to Mormon plural marriage in Utah. Homesteading accelerated the rapid, often violent, transformation of western environments. Perceiving this transformation, federal officials began setting aside natural preserves such as Yellowstone, often clashing with Native Americans who wished to hunt there.

Conflicts led to the dispossession of Native American lands. During the Civil War, whites clashed with the Sioux and their allies. Grant’s peace policy sought to end this conflict by forcing Native Americans to acculturate to European-style practices. Indian armed resistance continued through the 1880s, ending with Geronimo’s surrender in 1886. Thereafter, Native Americans survived by secretly continuing their traditions and selectively adopting white ways. Due in part to the determined military conquest of this period, the United States claimed a major role on the world stage. Frontier myths shaped Americans’ view of themselves as rugged individualists with a unique national destiny.