Between 1870 and 1920, 20 million Europeans immigrated to the United States, with half a million Chinese and Japanese also immigrating to the West Coast. This mass immigration, combined with migration from rural to urban areas, led cities to grow rapidly but also experience overcrowding, disease, and other problems. During this Gilded Age and Progressive Era, reformers sought to address these issues and problems with capitalism through progressivism, pushing for social welfare, moral reform, economic reform like regulating railroads and child labor laws, and government efficiency. Teddy Roosevelt championed many progressive causes as president from 1901-1909 like conservation and trust-busting.