Two hundred and fifty years ago, when the American West was still largely uncharted and George Washington was commanding the Continental Army, artists and explorers used watercolors to map the country’s rivers and mountain ranges—from the Hudson River Valley to the Grand Canyon and Yosemite. By the 19th century, these works grew in scale and began to incorporate narrative and character. This exhibition, drawn from the Corcoran Collection, presents 30 watercolors that date back to the country’s earliest days. —Elena Clavarino