The Short Answer
The authoritative source is the BLM's own Mineral & Land Records System (MLRS) — it's the official record of every active and historical mining claim in the country. The catch: it's built for looking up a specific claim by serial number or legal description, not for browsing a map to see what's claimed in an area you're curious about. For that, you need a map-based tool synced to the same underlying records.
Why This Matters Before You Stake — or Even Show Up
Staking a claim on ground that's already actively claimed doesn't give you any rights to it. At best your filing gets rejected; at worst you end up in a genuine conflict with the existing claimant over ground you never actually had a legal shot at. If you're buying, inheriting, or taking over someone else's claim, you need to independently confirm it's actually valid and in good standing before you treat it as real — a claim can look active on an old map and still have quietly gone void (more on exactly how that happens in next week's post). And even if you have zero interest in staking anything, knowing whether ground is claimed tells you whether casual metal detecting or panning there might run into an active claim holder's operations.
Here's a scenario that plays out more often than people expect: someone finds an old topo map or a decades-old prospecting guide pointing to a promising stretch of creek, drives out, and starts working it — only to find out later that a claim was staked on that exact spot two years ago and is very much active. Old references don't update themselves. The ground a book or a map described as "open" in 1995, or even five years ago, may not be open today, and the only way to know for certain is to check current status, not historical reputation.
Active vs. Historical: What You're Actually Searching For
When you check an area, you'll generally find one of three things: it's unclaimed, it has an active claim on it, or it has historical (expired/closed) claims on record. Historical claims are worth paying attention to, not skipping past — they're often the more interesting search target, since they mark ground someone already thought was worth working, and the reason it's open again is usually administrative (a lapsed fee, a missed filing) rather than the ground turning out to be worthless. Distinguishing active from historical at a glance is exactly what a map-based tool is for; MLRS will tell you the same thing, but only once you already have a specific claim to look up.
The Official Record: BLM's MLRS
MLRS is the real system of record — every claim's serial number, status, claimant of record, and filing history lives here, and it's what BLM's own state offices use internally. If you already have a claim name or serial number, this is the definitive way to confirm its status. What it isn't built for is the question most people actually have: "what's claimed in this general area?" MLRS doesn't give you a map to browse — you need to already know roughly what you're looking for.
Community Tools: Useful, But Not Official
You'll come across community-run resources like MyLandMatters.org, a volunteer educational project that maps claim data pulled from MLRS. It's a genuinely useful visual reference, and worth knowing about — but it's not a BLM product, updates run on roughly a two-week cycle by volunteer effort, and it shouldn't be treated as the authoritative record for anything you're about to act on.
Does onX Show Mining Claims?
A lot of people already using onX Hunt or onX Offroad for land-ownership and hunting-access layers assume it covers this too. It doesn't, really — onX's map layers are built around private/government land boundaries and hunting-access data, not a dedicated mining-claims layer. It can tell you who manages the land; it's not designed to show you where active or historical claims actually sit on it.
The Fastest Way: A Purpose-Built Claims Map
This is the exact gap a dedicated mining-claims map fills: active and historical claims layered directly onto a real map you can browse by area, synced on a regular schedule from BLM's own MLRS records rather than an occasional volunteer update — so you're looking at the same underlying data BLM itself works from, without having to already know a serial number to find it.
Check Your State
Claim density and how much ground is actively staked varies a lot state to state. Staked Maps currently covers active and historical claims across Alaska, Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, South Dakota, Utah, Washington, and Wyoming — each state page has current claim counts and a live map for that state specifically.