United States and Imperialism Historian Frederick Turner said, that "frontier has gone, and with its going has closed the first period of American history." Continental America had been settled by the turn of the century. Some say it is time for America to have a new frontier and that it might be found overseas. During the turn of the century, the United States become very involved in the affairs of the world. The United States would annex Hawaii and control the Philippines after the Spanish-American War. They would also build a canal in Panama to connect the Pacific and Atlantic Ocean. These actions caused