APN is short for Assessor Parcel Number, which is a unique number that a county tax assessor assigns to each plot of land. The number is used to keep track of land ownership and property taxes.

Often you can visit your county tax assessor’s website and view details about each parcel of land using the APN. Information tracked by the county may include size of the plot, age of the improvements (home) on the lot, current tax rate and sales history.