Jefferson County is a county in Kentucky, United States, on the Ohio River about 100 miles southwest of Cincinnati. It had a population of 782,969 at the 2020 census, an estimated 795,222 by 2024, and covers 398 square miles (1,030 km2) centred near 38°11′N 85°40′W.<\/p>\n
Louisville is the county seat, and since 2003 the county and the city have shared one government — Louisville\/Jefferson County Metro; its postal code is 40202. Consolidation merged county government into the city, but roughly 81 smaller home-rule cities, among them St. Matthews, Jeffersontown, Shively, Middletown, Anchorage and Prospect, stayed separately incorporated inside the county line. Jefferson County runs on Eastern time. Its FIPS code is 21111.<\/p>\n
Jefferson County works on two tiers. Louisville\/Jefferson County Metro Government runs county-wide services — police dispatch, roads, courts — across the whole 398 square miles, and its “balance” area, meaning everywhere outside the smaller cities, counted 633,045 residents in 2020. Layered inside that same boundary, about 81 smaller cities kept the mayor, council and zoning powers they held before the merger; several, including St. Matthews and Jeffersontown, run their own police departments. The table below lists the balance-area count for Louisville plus the 23 largest of the smaller cities, ranked by 2020 population; the rest run from a few hundred residents down to single-block cities of a few dozen.<\/p>\n
| Place<\/th>\n | Type<\/th>\n | Pop.<\/th>\n | ZIP<\/th>\n<\/tr>\n<\/thead>\n |
|---|---|---|---|
| Louisville<\/td>\n | City · seat<\/td>\n | 633,045<\/td>\n | 40202 & others<\/td>\n<\/tr>\n |
| Jeffersontown<\/td>\n | City<\/td>\n | 28,474<\/td>\n | 40299 & others<\/td>\n<\/tr>\n |
| St. Matthews<\/td>\n | City<\/td>\n | 17,534<\/td>\n | 40207<\/td>\n<\/tr>\n |
| Shively<\/td>\n | City<\/td>\n | 15,636<\/td>\n | 40216<\/td>\n<\/tr>\n |
| Lyndon<\/td>\n | City<\/td>\n | 11,008<\/td>\n | 40222<\/td>\n<\/tr>\n |
| Middletown<\/td>\n | City<\/td>\n | 9,706<\/td>\n | 40243<\/td>\n<\/tr>\n |
| Douglass Hills<\/td>\n | City<\/td>\n | 5,456<\/td>\n | 40243<\/td>\n<\/tr>\n |
| Hurstbourne<\/td>\n | City<\/td>\n | 4,683<\/td>\n | 40222<\/td>\n<\/tr>\n |
| Prospect<\/td>\n | City<\/td>\n | 4,592<\/td>\n | 40059<\/td>\n<\/tr>\n |
| Indian Hills<\/td>\n | City<\/td>\n | 2,860<\/td>\n | 40207<\/td>\n<\/tr>\n |
| Graymoor-Devondale<\/td>\n | City<\/td>\n | 2,853<\/td>\n | 40222<\/td>\n<\/tr>\n |
| Anchorage<\/td>\n | City<\/td>\n | 2,500<\/td>\n | 40223<\/td>\n<\/tr>\n |
| Windy Hills<\/td>\n | City<\/td>\n | 2,427<\/td>\n | 40207<\/td>\n<\/tr>\n |
| Hurstbourne Acres<\/td>\n | City<\/td>\n | 1,957<\/td>\n | 40220<\/td>\n<\/tr>\n |
| St. Regis Park<\/td>\n | City<\/td>\n | 1,438<\/td>\n | 40220<\/td>\n<\/tr>\n |
| Audubon Park<\/td>\n | City<\/td>\n | 1,433<\/td>\n | 40213<\/td>\n<\/tr>\n |
| West Buechel<\/td>\n | City<\/td>\n | 1,370<\/td>\n | 40218<\/td>\n<\/tr>\n |
| Coldstream<\/td>\n | City<\/td>\n | 1,295<\/td>\n | 40245<\/td>\n<\/tr>\n |
| Beechwood Village<\/td>\n | City<\/td>\n | 1,280<\/td>\n | 40207<\/td>\n<\/tr>\n |
| Barbourmeade<\/td>\n | City<\/td>\n | 1,216<\/td>\n | 40241<\/td>\n<\/tr>\n |
| Woodlawn Park<\/td>\n | City<\/td>\n | 947<\/td>\n | 40207<\/td>\n<\/tr>\n |
| Lynnview<\/td>\n | City<\/td>\n | 945<\/td>\n | 40213<\/td>\n<\/tr>\n |
| Seneca Gardens<\/td>\n | City<\/td>\n | 674<\/td>\n | 40205<\/td>\n<\/tr>\n |
| Glenview<\/td>\n | City<\/td>\n | 596<\/td>\n | 40025<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n Two pairs are easy to mix up. Hurstbourne and Hurstbourne Acres are separate cities that share a name root and sit close together off Shelbyville Road, but each keeps its own charter and council. Graymoor-Devondale is itself a merger of two older subdivisions, Graymoor and Devondale, that consolidated into one city rather than staying two — it is not related to the county-wide Louisville Metro consolidation of 2003.<\/p>\n ZIP Codes<\/h2>\nJefferson County’s ZIP codes span 40201 to 40299, more than 40 in active use, because the U.S. Postal Service assigns codes by delivery route rather than city charter — several of the smallest cities have no ZIP of their own and share whichever code covers their block.<\/p>\n Geography<\/h2>\nJefferson County sits in Kentucky’s Outer Bluegrass region on the south bank of the Ohio River, which forms the state line with Indiana. Of the county’s 398 square miles, 380 square miles (980 km2) is land and 17 square miles (44 km2) is water. Beargrass Creek and Floyds Fork are the two largest interior waterways; the Falls of the Ohio, the only natural obstruction on the entire river, sits at Louisville’s downtown riverfront. Frederick Law Olmsted’s late-19th-century park system — Cherokee, Iroquois and Shawnee parks, linked by parkways — still shapes how the county’s older neighborhoods are laid out.<\/p>\n Jefferson County borders Oldham County to the northeast, Shelby County to the east, Spencer County to the southeast and Bullitt County to the south. Across the Ohio River to the north and west lie Clark County, Indiana, Floyd County, Indiana, and Harrison County, Indiana.<\/p>\n Demographics<\/h2>\nThe county’s population was 782,969 at the 2020 census, up to an estimated 795,222 in 2024, and remains the most populous in Kentucky — more than double second-ranked Fayette County. Louisville’s balance area (633,045) and Jeffersontown (28,474) are the two largest population centers. Median household income was $54,357 (ACS 5-year estimate), below Kentucky’s statewide figure of $61,100 (2023). Population density across the 380 square miles of land works out to roughly 2,060 people per square mile, though it varies sharply between the dense urban core and the county’s still-rural southwestern corner.<\/p>\n Economy & Local Life<\/h2>\nUPS runs its Worldport global air-sorting hub at Louisville Muhammad Ali International Airport, the company’s single largest employment site, with tens of thousands of workers on rotating shifts. Ford operates two assembly plants in the county, the Kentucky Truck Plant and Louisville Assembly Plant, together employing thousands more. Humana is headquartered downtown, and GE Appliance Park anchors manufacturing on the east side near Jeffersontown, where Bluegrass Commerce Park alone hosts roughly 850 businesses and 38,000 jobs. Healthcare is a major employer too, led by Norton Healthcare, Baptist Health and the University of Louisville’s teaching hospitals. The county’s best-known annual event is the Kentucky Derby at Churchill Downs, run the first Saturday in May and capped by the two-week Kentucky Derby Festival.<\/p>\n History<\/h2>\nVirginia’s General Assembly created Jefferson County in June 1780, one of the three original Kentucky counties formed that year alongside Fayette and Lincoln, and named it for Thomas Jefferson, then Virginia’s governor. Louisville itself was founded two years earlier, in 1778, when George Rogers Clark established a settlement at the Falls of the Ohio to support his campaign against British forts in the Illinois Country. The county was among Kentucky’s original nine at statehood in 1792. The 1937 Ohio River flood, the worst in the region’s recorded history, put roughly 70 percent of Louisville underwater and reshaped the city’s flood-control infrastructure for decades after. In 2003, after decades of debate, city and county governments merged into Louisville\/Jefferson County Metro Government, while the roughly 81 smaller incorporated cities voted to keep their own charters.<\/p>\n Getting There<\/h2>\nInterstates 64, 65 and 71 converge downtown at what locals call Spaghetti Junction; two beltways, I-264 (the Watterson Expressway) and I-265 (the Gene Snyder Freeway), ring the urban core and the outer suburbs. No interstate bypasses the county entirely — all three mainlines pass through it.<\/p>\n
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