The state of Washington is located in the northwest corner of the continental United States and features a predominately mountainous terrain. Mining was the main driver of Washington’s economy in the 19th century, and the discovery of gold in Alaska during the early 20th century sparked the growth of Seattle. The city’s location made it a perfect departure point for those hoping to strike it rich in the northern frontier. In modern times, Washington has become a manufacturing hub for the aerospace and technology industries. The cities of Seattle, Tacoma, and Everett in the Puget Sound contain a significant portion of Washington’s commercial development. The Columbia River has long been at the heart of Washington’s economy as a source of transportation, fishing, hydroelectric power, and irrigation. Other significant contributors to Washington’s economy include wheat, aluminum, and tourism.