After the Great Seattle Fire of June 6, 1889 new construction was required to be of masonry, and the town’s streets were regraded one to two stories higher. Pioneer Square had originally been built mostly on filled-in tidelands and often flooded. The new street level also kept sewers draining into Elliott Bay from backing up at high tide. For the regrade, the streets were lined with concrete walls that formed narrow alleyways between the walls and the buildings on both sides of the street, with a wide "alley" where the street was. The naturally steep hillsides were used, and through a series of sluices material was washed into the wide "alleys," raising the streets to the desired new level, generally higher than before, in some places nearly. At first, pedestrians climbed ladders to go between street level and the sidewalks in front of the building entrances. Brick archways were constructed next to the road surface, above the submerged sidewalks. Pavement lights were installed over the gap from the raised street and the building, creating the area now called the Seattle Underground. When they reconstructed their buildings, merchants and landlords knew that the ground floor would eventually be underground and the next floor up would be the new ground floor, so there is very little decoration on the doors and windows of the original ground floor, but extensive decoration on the new ground floor. Once the new sidewalks were complete, building owners moved their businesses to the new ground floor, although merchants carried on business in the lowest floors of buildings that survived the fire, and pedestrians continued to use the underground sidewalks lit by the pavement lights embedded in the grade-level sidewalk above. In 1907, the city condemned the Underground for fear of bubonic plague, two years before the 1909 World Fair in Seattle. The basements were left to deteriorate or were used as storage. Some became illegal flophouses for the homeless, gambling halls, speakeasies, and opium dens. Only a small portion of the Seattle Underground has been restored and made safe and accessible to the public on guided tours. In 1965, local citizen Bill Speidel established "Bill Speidel's Underground Tour," which operates to this day.
