The streets of Philadelphia mainly follow a grid plan, one of the first such lay-outs used in a North American city. The grid plan originated in 1682, when William Penn founded Philadelphia and appointed Thomas Holme as his surveyor. Using , Penn planned a system of organized streets to facilitate future growth. Since Penn survived the Great Fire of London and wanted to avoid similar catastrophes, he laid out streets wider than usual. Penn planned the city to stretch between the Delaware and Schuylkill Rivers, and his grid plan of present-day Center City followed a 22-by-8-block pattern. The plan included a large square in the center of the town (present day location of Philadelphia City Hall), and four public squares near each corner of the city.