On June 6, 1889, a carpenter’s glue pot helped set downtown Seattle on fire. The rebuilding that followed left something unexpected: former sidewalks and storefront entrances beneath the modern city.

A small accident, a spreading fire

The fire began in a woodworking shop near Front Street—today’s First Avenue—and Madison Street. According to the Museum of History & Industry, an overheated glue pot boiled over, igniting nearby wood shavings and other flammable material.

Seattle’s wooden buildings, boardwalks and docks gave the flames plenty of fuel. The city’s patchwork private water system could not deliver enough water pressure to contain the blaze.

Over roughly 18 hours, the fire devastated about 100 acres of the business district and waterfront.

Rebuilding above the old level

Seattle rebuilt rapidly, using brick and stone throughout much of the burned commercial district. Many of Pioneer Square’s distinctive masonry buildings date to this rebuilding.

The reconstruction also provided an opportunity to address longstanding drainage problems and uneven street grades. Portions of the streets were raised.

Retaining walls supported the higher roadways, while spaces remained between those walls and neighboring buildings. These spaces, called areaways, eventually lay beneath the new sidewalks. Some former ground-floor entrances and sidewalks ended up below the new street level.

Windows beneath your feet

The lower spaces did not immediately become abandoned ruins. People continued using some of them, and glass prisms installed in the sidewalks above admitted daylight.

Those sidewalk lights remain one of Pioneer Square’s most distinctive details: windows that people walk across.

Over time, many lower-level spaces were closed or used for storage. Portions survive today as the Seattle Underground.

What actually lies below

Seattle did not bury an intact city in a single construction project. Its underground developed through rebuilding, street regrading and changes to sidewalks and building entrances.

That makes the surviving spaces more interesting: they are physical traces of a city changing its own ground level.

A workshop accident helped destroy Seattle’s commercial center. The city rebuilt—and left pieces of its earlier street life underneath.