Literally the MAF is a HUGE file full of every address that is, or ever has been, reported to the Census Bureau. The MAF in its current format was originally create for the Census 2000. It basically grew out of the 1990 Address Control File combined with the U.S. Postal Service’s Delivery Sequence File (DSF). This is constantly updated for use in conducting the decennial census, along with a host of other Census Bureau surveys, like the American Communities Survey for example.
There are nearly 279 million addresses in the MAF for the U.S. These are updated twice a year, mainly through the US Postal Service DSF. Interestingly, if an address get's demolished or changed, while it may disappear from the active MAF, it actually isn't deleted. It still is listed as an address that had existed. So even though the address has been corrected (due to a demolition or, say, due to an incorrectly provided address in the past), the old address - good, bad, or indifferent - remains in the records. this allows the Bureau to have a full and complete history of addresses from an area.
