Government Land Office maps (GLOs) are a result of the effort to survey all United States public lands before settlement. Starting in 1812 land was divided into square six mile blocks called townships, then subdivided into sections and ranges. Each subdivided area was surveyed and given its own map or GLO. During this process surveyors were required to indicate cultural resources such as roads and Indian trails and standardized symbols were used to represent geographic features. These GLOs are now maintained by the Bureau of Land Management as part of the official Land Status and Cadastral Survey records. As land was divided into parcels of individual ownership additional cadastral survey maps were created over time. For this reason there are often multiple GLOs or "cadastral survey maps" for one township / range, generally numbered one through four. For this seamless GLO layer, DAHP focused solely on the more historical GLOs which were usually listed as image number one or two for that specific township / range in the BLM Cadastral Survey records. In some cases no GLOs were available for review. Such areas included National Forest Lands, National Parks, Indian Reservations, and remote wilderness areas.