December 1861 and January 1862 brought about devastating floods that placed the future of the city in doubt . In order to resolve the situation , the city residents agreed that additional levee construction was necessary . However , the city was divided between camps that supported a relatively small grading of a few feet to raise the city just above the rivers ' cresting levels and those that supported a substantial grading to accommodate basements in city businesses . In the upcoming election of 1863 , the level at which the city should be raised became a primary factor ; a candidate that supported high-level grading won , and high-level grading renovation proceeded . Earth was removed from a dangerous bend nearby the confluence of the two rivers and used to raise city blocks in 1868 ; the city 's sidewalks , until construction was finally finished , were uneven because neighbors of raised city blocks often remained at the pre-construction level . After the filled regions beneath buildings had settled , new streets had to be paved . While planking had been used in the past , newly raised streets chose either the smooth ( though indurable ) Nicolson pavement or the easily dirtied ( though durable ) cobblestone pavement . Grading and paving processes were fully completed by 1873 , leaving the first floors of many buildings at the time as basements and leaving second floors as new main floors . Today , this system of 19th-century basements is known as the Sacramento Underground
devastating floods
Great Flood of 1862
History of Sacramento, California