The Dome That Gravity Holds: Washington's Capitol

There are five self-supporting masonry domes of any size in the world. The largest is Michelangelo's dome over Saint Peter's Basilica in Rome. The second is Wren's dome over Saint Paul's Cathedral in London. The third and fourth are in Florence and Mumbai. The fifth is in Olympia, Washington.

The Legislative Building's dome rises two hundred eighty-seven feet from the ground. It is the tallest self-supporting masonry dome in North America, and when it was finished in nineteen twenty-six, it was a genuine feat of construction. Two New York architects named Walter Wilder and Harry White won the design competition in nineteen eleven. Both had trained in the office of McKim, Mead and White, the firm responsible for some of the most ambitious classical buildings in American history. What they produced for Olympia was a dome set above a colonnade of Corinthian columns, loosely in the manner of Saint Peter's, adapted for a hilltop capital looking out over an inlet on the far northwest edge of the country.

To assemble the dome, masons fitted together more than fourteen hundred individual stones. They finished on October thirteenth, nineteen twenty-six. The completed dome weighs thirty point eight million pounds. Wilder and White designed it to be held in place by gravity alone. No bolts. No fasteners. The stones press against each other under their own mass, and the mass holds.

Governor Roland Hartley dedicated the completed Legislative Building on March twenty-eighth, nineteen twenty-eight. Construction had cost just under seven point four million dollars.

The dome shifted during the two thousand one Nisqually earthquake. The building closed for more than three years for repairs. The dome still stands on nothing but gravity and stone.