The Cathedral is the sixth largest in the world and the second largest in the United States. The one story porch projecting from the south transept has a large portal with a carved tympanum. This portal is approached by the Pilgrim Steps, a long flight of steps 12 m (40 ft) wide. The primary building material is gray Indiana limestone; some concrete and structural steel are used sparingly. The building abounds in architectural sculpture, wood carving, mosaics, wrought iron, and many other works of art, including over two hundred stained glass windows. Most of the decorative elements have Christian symbolism or are memorials to famous persons or events.
The plan for a national cathedral began in 1792 when the Plan of the Federal City set aside land for a "great church for national purposes." The National Portrait Gallery now occupies that site. A century later in 1891, a meeting was held to renew plans for the cathedral. In 1893 the Protestant Episcopal Cathedral Foundation of the District of Columbia was granted a charter from Congress to establish the cathedral, and the site on Mount Saint Albans was chosen. Bishop Satterlee chose Frederick Bodley, England's leading Anglican church architect, as the head architect. Henry Vaughan was selected to be the supervising architect.
Construction started in 1907 with a ceremonial address by President Theodore Roosevelt. When construction of the cathedral resumed after a brief hiatus for World War I, both Bodley and Vaughan had passed away; American architect Philip Hubert Frohman took over the design of the cathedral and is known as the principal architect. The Cathedral has been the location of many significant events, including the funeral services of Woodrow Wilson and Dwight Eisenhower. Its pulpit was the last one from which Martin Luther King, Jr spoke prior to his assassination. The Cathedral is the burial place of many notable people, including Woodrow Wilson, Helen Keller, Admiral George Dewey, Bishop Satterlee and the architects Henry Vaughan and Philip Frohman.