Leaving the region of the hills and descending from their crescent-shaped expanse, we find a broad extent of low ground, sloping gently toward the bay. On this low-lying flat was built all of San Francisco’s business houses, all its principal hotels and a large part of its tenements and poorer dwellings. It was here that the earthquake was felt most severely and that the fire started which laid waste the city.
Rarely has a city been built on such doubtful foundations. The greater part of the low ground was a bay in 1849, but it has since been filled in by the drifting sands blown from the ocean side by the prevailing west winds and by earth dumped into it. Much of this land was “made ground.” Forty-niners still alive say that when they first saw San Francisco the waters of the bay came up to Montgomery Street. The Palace Hotel was in Montgomery Street, and from there to the ferry docks—a long walk for any man—the water had been driven back by a “filling-in” process.
This is the district that especially suffered, that south of Market and east of Montgomery Streets. Nearly all the large buildings in this section are either built on piles driven into the sand and mud or were raised upon wooden foundations. It is on such ground as this that the costly Post Office building was erected, despite the protests of nearly the entire community, who asserted that the ground was nothing but a filled-in bog.
In none of the earthquakes that San Francisco has had was any serious damage except to houses in this filled-in territory, and to houses built along the line of some of the many streams which ran from the hills down to the bay, and which were filled in as the town grew—for instance, the Grand Opera House was built over the bed of St. Anne’s Creek. A bog, slough and marsh, known as the Pipeville Slough, was the ground on which the City Hall was built, and which was originally a burying ground. Sand from the western shore had blown over and drifted into the marsh and hardened its surface.
When the final grading scheme of the city was adopted in 1853, and work went on, the water front of the city was where Clay Street now is, between Montgomery and Sansome Streets. The present level area of San Francisco of about three thousand acres is an average of nine feet above or below the natural surface of the ground and the changes made necessitated the transfer of 21,000,000 cubic yards from hills to hollows. Houses to the number of thousands were raised or lowered, street floors became subcellars or third stories and the whole natural face of the ground was altered.
Through this infirm material all the pipes of the water and sewer system of San Francisco in its business districts and in most of the region south of Market street were laid. When the earthquake came, the filled-in ground shook like the jelly it is. The only firm and rigid material in its millions of cubic yards of surface area and depth were the iron pipes. Naturally they broke, as they would not bend, and San Francisco’s water system was therefore instantly disabled, with the result that the fire became complete master of the situation and raged uncontrolled for three days and nights.