Marion County, Missouri

Marion County is a county in Missouri, United States, in the northeastern corner of the state along the Mississippi River. It had a population of 28,525 at the 2020 census and covers 444 square miles (1,150 km2) centred near 39°49′N 91°37′W.

Palmyra is the county seat, and its postal code is 63461. The county has two full incorporated cities — Hannibal and Palmyra — plus the small city of Maywood, a share of Monroe City (whose main body lies in neighboring Monroe County), and roughly two dozen unincorporated communities and rural hamlets. Marion County sits in the Central time zone.

Towns & Villages in Marion County

Marion County has three incorporated cities and about three dozen unincorporated communities and crossroads settlements — several are little more than a church, a cemetery and a cluster of farms. Unlike most third-class Missouri counties, Marion has two courthouses: one in the seat, Palmyra, and a second in Hannibal, its largest city.

Hannibal itself straddles two counties: the bulk of the city lies in Marion County, but its southern edge extends into Ralls County. Monroe City works the same way in reverse — most of that city sits in Monroe County to the west, with only a small share crossing into Marion.

ZIP Codes

• 63401 — Hannibal
• 63461 — Palmyra
• 63454 — Maywood
• 63463 — Philadelphia
• 63471 — Taylor

Marion County’s five ZIP codes cover the county’s two courthouse cities and three small outlying communities; most of the smaller hamlets on the settlement list share a ZIP with the nearest of these post office towns rather than having their own.

Geography

Marion County lies where the Mississippi River forms the state’s eastern border, and the county’s terrain runs from the river’s bluffs and bottomland in the east to rolling farmland further inland. The North River and South River both cross the county and feed the Mississippi; the old settlement names “North River” and “South River” on the list above mark communities that grew up along their banks. The county is bordered by Lewis County to the north, Shelby County to the west, Monroe County to the southwest, Ralls County to the south, and by Pike County, Illinois to the southeast and Adams County, Illinois to the northeast, both across the Mississippi.

Demographics

Marion County’s population was 28,525 at the 2020 census. Hannibal is by far the largest community at 17,108 residents, followed by Palmyra as the county seat; both together account for most of the county’s people, with the remainder spread across Maywood, the Marion County portion of Monroe City, and the unincorporated communities. Missouri’s statewide median household income (2023 ACS) is $68,545; Marion County, a mostly rural county built around two mid-sized river towns, typically runs below that figure. Density works out to roughly 65 people per square mile across the county’s 437 square miles of land.

Economy & Local Life

Hannibal anchors the county’s economy. Hannibal Regional Hospital and Hannibal Clinic are major employers, alongside manufacturers BASF Chemical Corporation, General Mills, and Watlow Electric Manufacturing Co. Hannibal-LaGrange University, a four-year Christian liberal arts school, is also based in the city. Tourism built around Mark Twain — Hannibal was his boyhood home, and the town markets itself heavily on that connection — draws visitors to the historic downtown along the river. National Tom Sawyer Days, held each Fourth of July week, is the county’s best-known annual event, with a fence-painting contest, a frog-jumping contest and fireworks over the river. Away from Hannibal, the county’s economy is agricultural, historically built on tobacco and now mixed row-crop and livestock farming.

History

Marion County was organized on December 23, 1826, and named for General Francis Marion, the “Swamp Fox” of the American Revolutionary War, a South Carolina native. Before it was organized as a county, the area was known informally as “Two Rivers Country,” a reference to the North River and South River. The county’s two-courthouse arrangement, in Palmyra and Hannibal, is unusual among Missouri’s third-class counties and reflects Hannibal’s early growth into the area’s dominant town even though Palmyra kept the official seat.

Getting There

US Highways 24, 36 and 61 and Interstate 72 all cross Marion County, meeting at or near Hannibal.

• Quincy, Illinois — 5 miles northeast of Hannibal
• Monroe City — 18 miles southwest of Hannibal
• Palmyra — 10 miles west of Hannibal
• Columbia, Missouri — about 100 miles southwest

The nearest commercial airport is Quincy Regional Airport in Quincy, Illinois, just across the Mississippi from Hannibal.

Frequently Asked Questions

Where is Marion County, Missouri?
It is in the northeastern corner of the state, on the Mississippi River across from Illinois, roughly 100 miles north of St. Louis.

What is the population of Marion County?
28,525 at the 2020 census.

How big is Marion County?
444 square miles (1,150 km2), of which 437 square miles is land and 7.4 square miles is water.

What is the county seat of Marion County?
Palmyra is the county seat, though Hannibal, the county’s largest city, also has its own courthouse.

How many towns are in Marion County?
Three incorporated cities — Hannibal, Palmyra and Maywood — plus a share of Monroe City and roughly three dozen unincorporated communities.

What ZIP codes are in Marion County?
63401 (Hannibal), 63461 (Palmyra), 63454 (Maywood), 63463 (Philadelphia) and 63471 (Taylor).

Why is Hannibal famous?
Hannibal was the boyhood home of Mark Twain, and the city’s downtown and riverfront are built around that connection, including the annual National Tom Sawyer Days celebration each July.

More counties in this state: Towns and villages in Missouri.