Largest US Counties Designated Medically Underserved
PlainHealthAccess ranks US counties carrying an HRSA Medically Underserved Area (MUA) designation, sorted by total county population from the portal's source-vintaged HRSA dataset.
Research period:
Research question
Among the 2,798 US counties carrying an HRSA Medically Underserved Area designation, which have the largest resident population, and what does the geographic distribution of high-population MUA counties reveal about urban as well as rural access challenges?
Methodology
This ranking shows the top 10 US counties carrying an HRSA Medically Underserved Area (MUA) designation, sorted by total county population. Values are calculated from this portal's source-vintaged HRSA snapshot; the visible vintage identifies the data release behind the comparison.
Health Resources & Services Administration occasionally suppresses values for reasons of confidentiality, sample size, or quality control. A county with a missing or zero population figure is excluded from this ranking rather than shown as a zero, since treating a suppressed value as zero would misrepresent it. A later agency revision is reflected here only after a verified portal refresh; use HRSA's official tools when current designation status matters.
An MUA designation can apply to a whole county or to specific service areas within it, and the county-level Index of Medical Underservice (IMU) score does not reveal within-county variation, so a large, high-population county can still contain both well-served and underserved neighborhoods.
The second chart on this page shows the Index of Medical Underservice score for these same counties, a distinct measure where a lower score indicates greater underservice, so readers can compare county size against severity.
See the methodology page for the full data sourcing and update process.
Top 10 Largest US Counties Designated Medically Underserved (HRSA)
Current MUA-designated county population figures as of your visit
Index of Medical Underservice (IMU) for Those Same Counties
Lower IMU = more underserved; a different facet of the same top-10 counties in this source-vintaged portal snapshot
The ranked top 10
The table below shows all 10 ranked counties from this source-vintaged portal snapshot. Check HRSA directly when a current designation status matters.
| # | County | State | Population | MUA index |
|---|---|---|---|---|
| 1 | Los Angeles | CA | 10,014,009 | 47.9 |
| 2 | Cook | IL | 5,275,541 | 35.1 |
| 3 | Harris | TX | 4,731,145 | 48.4 |
| 4 | Maricopa | AZ | 4,420,568 | 47.3 |
| 5 | San Diego | CA | 3,298,634 | 41.8 |
| 6 | Orange | CA | 3,186,989 | 46.7 |
| 7 | Kings | NY | 2,736,074 | 44.5 |
| 8 | Miami-Dade | FL | 2,701,767 | 28.4 |
| 9 | Dallas | TX | 2,613,539 | 45.8 |
| 10 | Riverside | CA | 2,418,185 | 48.8 |
Source: Health Resources & Services Administration, HRSA MUA Designation files with county-level Index of Medical Underservice scores, used in this source-vintaged portal snapshot.
Findings
Top entity in the ranking
The top-ranked record in this dataset is Los Angeles, with a population of 10,014,009. The full top-10 set is shown in the table above. Each value is calculated from the portal's source-vintaged dataset rather than hand-entered. A new Health Resources & Services Administration release requires a verified portal refresh before it appears here.
Distribution shape
The gap between the top-ranked record (10,014,009) and the 10th-ranked record (2,418,185) characterizes how concentrated the top of the distribution is. Where the top value is many multiples of the median value of the visible set, the population is highly concentrated, a small number of entities accumulate the bulk of the measured quantity. Where the top and bottom of the visible set are close together, the distribution is relatively flat across the top end. The full distribution beyond this top-10 cut is summarized in the aggregate context section below and explored in the linked entity profiles.
Aggregate context
These figures situate the top-10 ranking against the full population of MUA-designated counties: how many counties qualify in total, what the combined population is across all of them, and what the average per-county population looks like. Counties with a missing or zero population figure are excluded from this aggregate, consistent with the ranking above.
Source provenance
The records in this ranking originate from Health Resources & Services Administration, specifically the HRSA MUA Designation files with county-level Index of Medical Underservice scores. PlainHealthAccess preserves a stated source vintage rather than claiming a real-time agency lookup. The methodology page documents the source URL, vintage, and processing limits.
Why this ranking matters
Rankings like this one let a reader scan a population quickly and identify outliers, concentrations, and patterns that warrant deeper investigation. The detail pages linked from each entity in the table above give the full per-entity context: time-series history where available, related metrics from adjacent tables, and links onward to the underlying source records. The methodology page explains how an entity earns inclusion in the dataset and how the ranked metric is calculated at the source.
What this analysis cannot tell us
MUA designations follow HRSA's Index of Medical Underservice (IMU) score, which combines four indicators: provider-to-population ratio, percent of population below the federal poverty level, percent of population age 65 or older, and infant mortality rate. A county-level MUA designation may apply to the whole county or to specific service areas within the county. High-population MUA counties often contain affluent neighborhoods with strong access alongside underserved neighborhoods with structural access gaps, the county-level designation does not reveal this within-county variation. The MUA designation framework is one tool among several federal health-access measures and does not capture every dimension of access (transportation, language services, insurance coverage, after-hours availability). Designation does not equate to a measure of clinical care quality at any specific facility within the county.
Sources
- Health Resources & Services Administration, MUA Designation Files - https://data.hrsa.gov/tools/shortage-area/mua-find
Every figure on PlainHealthAccess is rendered directly from HRSA source data, no number is typed in by an editor. This ranking sorts MUA-designated counties by population from the portal's source-vintaged dataset. See our editorial standards & corrections policy, the methodology behind these numbers, review the public data changelog, or report a data issue for this page.