Fair example of Alonso Horton's map of downtown San Diego, surveyed by L.L. Lockling and engraved by G.T. Brown.
Lockling's map of the Horton addition is the birth certificate of modern San Diego. While a prior attempt had been made to develop the downtown area (New Town) prior to the Civil War, it was Horton's vision and energy which launched New Town on the path of developing into the first viable commercial development in San Diego County. The map consists of two parts, a subdivison map, showing all of the blocks and lots subdivided by Horton, extending from Upas Street in Mission Hills to O Street, which was probably never existed, the southern most east west running street in Downtown being Commercial Street, which is N Street on this map.
The upper right part of the map is a larger map of San Diego harbor, showing the relative position of Horton's Adition, which was then the only part of the City which had been actively subdivided for commercial and residential purposes.