On a warm afternoon in June 1889, a pot of boiling glue spilled over in a carpenter’s shop in downtown Seattle. The fire quickly spread and destroyed 25 blocks in the city center in less than 12 hours. Now, 137 years after the Great Seattle Fire, visitors to the Pioneer Square Preservation District can still explore the underground remains of old shops, sidewalks and archways.
Instead of simply clearing away the ashes and rubble, city leaders saw a chance to fix two major problems. The city often suffered from mud caused by high tides, and many streets were too steep or difficult to use. Officials passed a law requiring all new buildings to be made of brick or stone. City engineers also began a major rebuilding project that eventually buried the original street level deep underground. These spaces once formed the ground floors of businesses in Washington state’s growing timber and trading port.
According to historical records published by the Seattle Department of Transportation Areaways Program, the city has more than 100 documented areaways, most of them in the Pioneer Square Preservation District. Because of concerns about sanitation and the spread of disease, in 1907, city health officials closed the underground walkways to the public. To bring natural light into the dark passageways below, builders installed sidewalk vault lights. These lights used small, thick glass pieces called prisms, set directly into concrete sidewalks. Over time, exposure to moisture and air caused many of the clear glass prisms to turn purple. This color change resulted from a chemical reaction involving manganese oxide, which was added during glassmaking in the late 19th century. Research from the National Trust for Historic Preservation identifies these glass prisms as a special feature of Pioneer Square’s architecture. Preservation projects continue to focus on repairing leaking or damaged sidewalk vaults across the district. The underground spaces served many purposes over the years. In the late 19th and early 20th centuries, merchants used them to store goods, deliver coal through chutes and house engine rooms. The spaces remained locked away for decades. Some were used for illegal gambling halls or storage, while others were left untouched.
These hollow spaces beneath today’s sidewalks formed when property owners enclosed the gaps between their building fronts and the newly raised street walls.