People say "property records" as if it were one file. It is at least two, kept by two different county offices for two different reasons, and the difference explains most of the surprises in property data.
The assessor file
Every county assessor keeps a roll of parcels for one purpose: taxing them. The roll describes each parcel well enough to value it. That gives you the parcel number, the situs address, the owner of record and the owner's mailing address, the land use, the lot size, and for improved parcels the building characteristics: living area, year built, bedrooms, bathrooms, stories, and in some counties the roof, the exterior walls, the heating system, the garage and the pool. It also carries the assessed value and, in most states, the assessor's estimate of market value.
The assessor file is a snapshot. It says what the parcel looks like as of the last assessment cycle. It does not say what happened to the parcel, which is the recorder's job.
The recorder file
The county recorder, sometimes the clerk or the register of deeds, files documents. Deeds transfer ownership. Mortgages and deeds of trust create liens. Releases satisfy them. Lis pendens and notices of default begin foreclosure. Each document is indexed by date, type, the parties named and, usually, the parcel it affects.
The recorder file is a history. It tells you when the property last sold, for how much, to whom, and with what financing, and every event since. A transaction dataset is the recorder file filtered to deeds and joined to the assessor's parcel so the sale has an address and a house attached to it.
The parcel key
The assessor's parcel number is the join. Every deed, mortgage, permit, listing and valuation for a property can be keyed to it, which is why a national file that has done the keying properly lets you ask questions like "every home that sold in 2024 and pulled a roofing permit within a year" without matching addresses. Address matching is where property data projects go to die, because addresses are written a dozen ways and unit numbers are optional. A stable parcel identifier that survives the monthly refresh is the single most valuable thing a property data vendor provides.
What is reliably filled, and what is not
Coverage is a county story, not a national one. Some fields are near universal because every assessor needs them: the owner name, the mailing address, the lot size, the assessed value and the coordinates are filled on effectively every residential parcel in the country. Year built and living area are filled on most parcels nationally, with a handful of states well below that because their counties do not publish them.
The structure codes are the weak spot. Roof cover, construction type and exterior wall material come straight off the county's field card, and roughly half of counties either do not collect them or do not publish them. Nationally about half of residential parcels carry a roof cover code. Two neighboring states can sit at ninety-five percent and eight percent. A pool code is filled on a small minority of parcels, and that is a reporting rate, not a pool rate.
The practical rule: before you buy property data for a specific use, ask for the fill rate of the fields you need on the states you operate in, and ask what denominator was used. "Year built is ninety percent filled" means something different on all parcels, on residential parcels and on residential parcels with a building. We publish ours per state on the property coverage pages using residential parcels as the denominator, and we say so.
What changes between refreshes
An assessor file turns over slowly and a recorder file turns over constantly. In a typical year a few percent of residential parcels record a deed, and a comparable share record a new mortgage or a release. Assessed values change once a year in most states, on the assessor's cycle. New construction appears as parcels with a recent year built, and splits and merges retire old parcel numbers and create new ones, which is why keys need a crosswalk rather than a simple overwrite.
A monthly refresh with flagged deltas is the right cadence for most uses. Daily matters for listings and for foreclosure filings, not for the roll.
How the record becomes useful
By itself an assessor row is inventory. It becomes something you can act on when it is joined. Join it to the recorder and you have tenure and equity. Join it to permits and you have condition history and a roof age. Join it to listings and you know whether the owner is trying to leave. Join the owner name to a consumer file and you have a phone that answers. Each join is a separate dataset on this site, and each shares the parcel key so the joins are exact.
Questions
Is property record data public?
Yes. Assessor rolls and recorder indexes are public records in every US state, with state-level limits on how some fields may be displayed or used. The work is in aggregating thousands of counties into one keyed file.
How often do property records change?
Recorder documents arrive daily. Assessor values change once a year on the county's cycle. A monthly refresh with flagged deltas covers most uses; listings and foreclosure filings are the exceptions that need daily.
What is the difference between assessed value and market value?
Assessed value is set for taxation and is often a statutory fraction of market value. Market value is what a buyer would pay, which an AVM estimates from recent sales.