The city of Two Harbors is the county seat and a major shipping point for iron ore on Lake Superior; it lies on two little bays, natural harbors, named Agate and Burlington Bays, the ore docks being on the western Agate Bay. Beach sand and gravel here contain frequent pebbles of banded chalcedony called agate. The city was platted in 1885 as Agate Bay, although its post office was known as Two Harbors when established in 1883; it was incorporated as a village March 9, 1888, and as a city February 26, 1907. The townsite of Burlington at Burlington Bay was platted in 1856, first incorporated on May 23, 1857, and later incorporated with Agate Bay as Two Harbors; Burlington had a post office, 1856-62. The first shipment of ore arrived from the Soudan Mine on July 31, 1884. It is the site of the Edna G., a tugboat owned by the Duluth, Missabe and Iron Range Railroad, built in 1896 and named for Edna Greatsinger, daughter of Jacob Greatsinger, president of the railroad; the tug was placed on the National Register of Historic Places in 1975 as the only steam-powered tug operating on a Great Lake. Segog, named for developer Ray F. Segog, is one of several additions to the city.