This document summarizes key political and economic developments in the United States from the 1870s to the early 1900s. It discusses the stable two-party system, the agrarian populism movement, economic crises and debates over currency standards in the 1890s. It also covers the Spanish-American War of 1898 that resulted in U.S. control of Puerto Rico, Guam and the Philippines, sparking debates over imperialism. The emergence of the U.S. as a world power with overseas colonies is examined.