What are Plat Maps

Did you ever wonder why today’s towns look the way they do? The look of the downtown area, with its square blocks, originates centuries ago, when the country was first dividing what would eventually become a large portion of the United States. Beginning in the late eighteenth century, these unexplored lands were surveyed under the Public Land Survey System. This is a rectangular survey system that required the platting of lands according to particular distance; it replaced earlier systems that measured a given piece of land according to its dimensions from landmarks, allowing for non-square parcels. The original city or village plat began with townships and sections of land, with each section being one mile square, and each township containing 36 such sections, for an area measuring six miles square.

Historic plat maps are maps, drawn to scale, showing the divisions of the city’s land. These show the individual blocks, and usually the individual lots after the blocks were subdivided for the purpose of selling land to settlers. This plat map was filed with the local government. Depending on the time of filing and the purpose of the plat map creation, this may be the local courthouse, the General Land Office, the local urban planning board, or some other government entity. After filing, each lot of land could be referred to either by reference to its block and lot numbers, as stated in the plat map, or to the portion of the section in which it lies, after the Public Land Survey System method. These plat maps may also be known as parcel maps, tax maps, landowner maps, lot and block survey system, or land survey maps. The creation of a plat map is an important step in the process of incorporating a town.

Plat maps are usually drawn as part of the process of incorporating a city, although there are several other reasons why a plat map may be filed. If a particular landowner purchases several adjacent parcels of land and consolidate them into a single parcel for legal purposes, a Plat of Consolidation may be filed. This requires the landowner to have a survey done of the property and a plat map drawn. A Plat of Subdivision is the opposite of this; a landowner is dividing land into smaller parcels, generally for the purpose of selling these parcels individually. Again, this process requires a survey and the drawing of a plat map.

When the plat map is filed, it is reviewed and approved by the local government. There may be multiple zoning rules governing the layout of a plat map; for example, in some areas, a plat map must contain a given amount of land set aside for green areas, schools, or other purposes rather than sold for housing or commercial purposes. The plat map must also designate roads and similar rights of way, and ensure that all parcels have access to a public right of way. In other words, there can be no parcel of land created in the middle of other lots with no access to a road or a right-of-way to access a road. This prevents the unethical process of selling landlocked parcels of land that can only be accessed via trespassing across other properties or via helicopter.

Charles Lee Iner
September 2009