 Hidalgo County is designated by the U.S. Census Bureau as the McAllen-Edinburg-Mission Metropolitan Statistical Area, which itself is part of the McAllen-Edinburg-Mission-Rio Grande City Combined Statistical Area with neighboring Starr County.According to the U.S. Census Bureau, the county has a total area of , of which are land and (0.8%) are covered by water.The northern part of the county has sandy and light loamy soils over deep reddish or mottled, clayey subsoils.