Mount Waldo, a small mountain in Frankfort, Maine, became the center of an important granite industry because its bare ledges and access to tidewater made quarrying practical in the early 19th century. The chief quarry on the mountain’s north spur used graded tracks and a cable road to move stone to a Marsh River wharf, where schooners carried it to eastern ports and inland cities. Mount Waldo’s medium-gray, coarse-grained granite was used in major American structures including the Washington Monument, the U.S. Senate Office Building, the Tomb of the Unknown Soldier, the United Nations Building, and Brooklyn Bridge piers. Quarrying ended by 1914, but the industrial remains still mark its significance.