From the colonial era, relations between European settlers and Native American nations have been complicated. In 1803 Congress authorized and funded an expedition led by Meriwether Lewis and William Clark for exploration of the region and for better knowledge about American Indians of the Northwest in order to develop trade. About 30 years later, the United States forced the removal of Native Americans from their lands to make way for white American settlement. Congress and the president made treaties with Native American nations, but those treaties were not always respected as the United States continued to expand into the west. After Native Americans enlisted and served in both World War I and World War II, Congress passed legislation to begin to address longstanding Native Americans claims against the United States Government.