Our knowledge of the physical layout of New York from the middle of the nineteenth century onward is due in large part to the advent of fire insurance maps and commercial atlases. Manhattan island had been mapped in various ways since it was first settled, but it was not until the beginning of the nineteenth century that large-scale specialized mapping began to be employed. The first significant effort was made by John Randel, whose large scale maps of most of Manhattan were used to create the street grid called for by the Commissioner's Plan of 1811. These maps focused on topography and property lines, paying relatively little attention to the buildings. It was not until the 1850s that detailed mapping of New York's buildings took place. Insurance companies had suffered massive losses in the 1835 fire that wiped out many of the smaller buildings. The surviving companies banded together, and in the late 1840s the English engineer William Perris was hired to make a new map of the city at the highly detailed scale of fifty feet to the inch. They were surveyed from scratch; every building perimeter was walked and measured and all aspects of their construction that could be relevant for fire protection were recorded via an elaborate system of colors and symbols. The first sets of the Perris maps were published in 1852, and a new set was undertaken almost immediately because they were so successful and the city was changing so quickly. Perris released new sets in 1855, 1857 and 1868. While waiting for new additions, subscribers to the maps were offered paper additions that could be pasted over outdated sections. The fire insurance maps were very profitable and were soon released by other publishers, who also began to offer detailed, general purpose atlases of the city. Among these were Matthew Dripps' 1867 Plan of New York City and Elisha Robinson's 1885 Atlas of the City of New York, both of which give us an important record of the changing city.