Harbor Island is the largest man-made island in the United States. Located in the mouth of Seattle’s Duwamish Waterway that empties into
Elliott Bay, the island was built by the Puget Sound Bridge and Dredging
company in 1909. The island was built from 24 million yards of earth
from the dredge spoils of the Duwamish River and the soil of Jackson Hill
and Dearborn Street re-grades. At 350 acres, it was the largest artificial
island in the world when it was built.
Filling in the vast tide flats south of
downtown Seattle, the dredging also created the area now occupied by Union
Station, King Street Station, Seattle's sports stadiums, and much of the
city's industrial base.
Growing resentment of railroad and
shipping monopolies led King County voters to create the Port of
Seattle in 1911, of which Harbor Island became a part of.
Harbor Island lost
its title as the world's largest man made island in 1938 when Treasure
Island in the San Francisco Bay was completed. However, in 1967,
Harbor Island was increased by additional fill to 395 acres and
regained its title. Though it continues to be the largest
artificial island in the United States, the Rokko Island in Japan is
now more than three times larger.
After World War II
the Port of Seattle diversified its activities with expansion of
Fishermen’s Terminal, the construction of Shilshole Bay Marina,
ambitious developments on Harbor Island, and the creation of
Seattle-Tacoma International Airport.
Over the years, the
island has been used for commercial and industrial activities
including ship building and repair, lead smelting, petroleum storage,
metal fabrication and containerized cargo shipping.
Fringed by wharves
and cranes, the island houses numerous warehouses, laboratories, other
industrial buildings, and railroad years. It is the Port of
Seattle’s major point of entry for cargo transferred from oceangoing
vessels to trucks and railcars.
Fisherman utilize the
waters surrounding Harbor Island primarily to catch shellfish and
There are no
residences on Harbor Island, but approximately 10,000 people live
within one mile of the site.
Both the West Seattle Bridge and the
Spokane Street Bridge pass over the island.
America, updated December, 2015.