Where the data comes from, and where it stops.

Source

Every holding on a county page comes from the Federal Communications Commission's Universal Licensing System (ULS), the public database of wireless licences. The FCC publishes complete weekly snapshots of ULS as downloadable files. We use those files, not a scrape of the search interface and not data from carriers or third parties.

County names, FIPS codes, county boundaries and ZIP Code Tabulation Areas come from the US Census Bureau. Band and channel arithmetic follows 3GPP TS 38.104 (NR-ARFCN) and TS 36.101 (EARFCN).

Weekly build

1. Fetch. The full ULS licence, market, lease and frequency tables are downloaded after the FCC's weekly publication.
2. Select. Active licences in the commercial mobile radio services are kept: 600 MHz, 700 MHz, Cellular, SMR, PCS, AWS, WCS, BRS and EBS, 3.45 GHz, CBRS priority access, C-band and the millimetre-wave bands.
3. Map to counties. Each licence's market area is expanded to the counties it covers. Partitioned licences are cut along the partition; disaggregated licences are split by frequency.
4. Attribute. Licensee entities are grouped under the carrier that controls them. Leases are attached to the blocks they cover.
5. Check. The build is compared with the previous week. Implausible swings, overlapping licences and unmapped areas stop the publish until a person has looked.
6. Publish. Pages, the JSON API and the change feed are regenerated together, so they never disagree.

Counting rules

• Five national operators. Totals are computed for Verizon, AT&T, T-Mobile, Dish / EchoStar and SpaceX. Every other licensee appears in the band plan and the table but has no total.
• MHz are uplink plus downlink. A paired 5 + 5 MHz block counts as 10 MHz. Overlapping records are merged, so the same frequency is never counted twice for one operator.
• Leases count for the lessee, and are not subtracted from the licensee. An operator is credited with what it is licensed for plus what it leases in. Spectrum it leases out still counts for it, so leased spectrum can appear in two operators' totals.
• FirstNet. Band 14 is licensed to the First Responder Network Authority and built and operated by AT&T. It is credited to AT&T and labelled.
• CBRS. Each Priority Access Licence counts as 10 MHz of high-band. PALs have no fixed frequency, so they appear in the table but not at a position on the band plan. General Authorized Access use is unlicensed and is not counted.
• Cellular. Where one cellular market block has different licensees in different parts of a county, it is counted once, for the licensee with the most cell sites in the county.
• Affiliates. Subsidiaries and designated entities are grouped under the operator that controls them. Licences held in trust pending a sale are labelled with the buyer and the trust.
• Band plan. Where several records cover a frequency, the strip shows a national operator's licence first, then a national operator's lease, then other licensees.

The four tiers

The industry often calls everything from 1 to 6 GHz "mid-band". We separate 2.3 – 6 GHz because those bands use much wider channels and reach a shorter distance, and lumping them with PCS and AWS hides the difference that matters most between carriers.

Known limits

• Licensed is not deployed. A licence permits transmission. It does not show that a carrier has built anything in a county, on which towers, or with what equipment.
• Not a coverage map. More spectrum generally means more capacity, but tower density, backhaul and terrain decide what you experience.
• Timing. The data is at most a week behind ULS, and ULS itself lags real-world deals: an announced sale does not appear until the FCC records the assignment.
• Leases as filed. Lease records are shown as the FCC lists them. A lease that has lapsed without a cancellation filing can still appear.
• Partitions without boundaries. Some partitioned licences are recorded without coordinates or a county list. They cannot be placed and are listed separately on the county pages they might touch, never counted.
• Partial coverage. A licence that reaches only part of a county is shown for the whole county and tagged.
• Private arrangements. Roaming agreements and network-sharing deals that are not filed with the FCC are invisible to us.
• Unlicensed and shared use. Wi-Fi bands, CBRS General Authorized Access and satellite-only allocations are outside the scope of the site.
• ZIP codes. ZIP lookup uses Census ZIP Code Tabulation Areas. A ZIP that crosses a county line resolves to the county containing most of its area.
• Errors. Mapping 176,526 records onto 3,221 counties is automated and will contain mistakes. Tell us when you find one.

Licence boundaries and MHz-POPs

The map's licence-boundary view and the bulk licence files draw each licence's own area rather than rounding it to counties. Population: US Census Bureau 2020 Census, Centers of Population (county and block-group files, 50 states + DC + PR): whole counties use the county count; a partly covered county sums the block groups whose centre of population lies inside the licensed area. MHz-POPs is that population multiplied by the licence's MHz.

In the bulk area files each licence lists full (counties covered entirely: a market id to look up in markets, or a list of FIPS codes) and part (counties covered partly, each pointing at a GeoJSON polygon in shapes).

• Market-based licences cover whole counties; coordinate-defined partitions and leases, and BRS/EBS site-based GSAs (35-mile circles split with co-channel neighbours along the perpendicular bisector), are drawn as the exact polygon clipped to each county.
• A county is listed only where the area covers at least 1% of the county or 1% of the area (the county view's rule), and a piece covering 99% or more of its county is listed as the whole county.
• Pieces are clipped to the Census 2020 1:500k cartographic county outlines, simplified to about 100 m and rounded to 4 decimals, so neighbouring pieces can show small gaps or overlaps.
• Population is the 2020 Census count; a partly covered county counts the block groups whose centre of population lies inside the area, so a piece can be off by part of a block group (typically 600 to 3,000 people).
• A BRS/EBS BTA licence covers its BTA minus co-channel site-based GSAs; a county where those GSAs take half or more is left out entirely, so the BTA holder's remainder there is not listed.
• A lease without partition records of its own is shown over its parent licence's area; cellular leases are really site-based pieces of the CMA, so this can overstate where a cellular lessee operates.
• Cellular licences are placed by whole CMA (cell-site CGSA contours are not modelled); where two licensees claim the same block in a county, the one with fewer cell sites there is secondary in that county (secondaryIn).
• approx: true marks a record whose area is uncertain: it has an exclusion the FCC records without coordinates, or a listed county where its recorded exclusions or co-channel GSAs leave nothing (shown before that subtraction); its area and population may be overstated.
• Partition areas the FCC records without coordinates (e.g. 'Iowa Study Area 33') are not mapped and not listed.
• A licence can appear more than once (one entry per partition, and per 2.5 GHz channel for BRS/EBS), each with its own area; MHz counts both directions of a paired block and a CBRS PAL counts as 10 MHz.

What is live and what is not

• Live: county pages, the JSON API and the MCP server, for 3,221 counties in the 50 states, DC and Puerto Rico, from FCC data dated October 4, 2026.
• Change feed: open assignment and transfer applications from the FCC's weekly application files, dated October 3, 2026. Week-to-week differences in the licence data are not listed yet.
• Not covered: Guam, the US Virgin Islands, American Samoa and the Northern Mariana Islands.

Independence

carrierdepth is published by Centurion Holdings Group LLC of Raleigh, North Carolina. It has no commercial relationship with Verizon, AT&T, T-Mobile, EchoStar, SpaceX or any other licensee, and none of them has reviewed or approved its contents. Carrier names are used only to identify who holds a licence.

The site is funded by display advertising served by Google AdSense. Advertisers do not choose, see in advance or influence what is published. See privacy and ads.

Corrections

If a county page disagrees with ULS, ULS is right and we want to know. Write to corrections@carrierdepth.com with the county and the call sign.