Plymouth County, Iowa

Plymouth County, Iowa
Location within the U.S. state of Iowa
Coordinates: 42°44′15″N 96°12′58″W / 42.737615°N 96.215973°W / 42.737615; -96.215973
Country United States
State Iowa
FoundedJanuary 15, 1851 (created)
October 27, 1858 (organized)
Named afterPlymouth, Massachusetts
SeatLe Mars
Largest cityLe Mars
Area
 • Total
863.668 sq mi (2,236.89 km2)
 • Land862.828 sq mi (2,234.71 km2)
 • Water0.840 sq mi (2.18 km2)  0.10%
Population
 (2020)
 • Total
25,698
 • Estimate 
(2024)
25,825
 • Density29.783/sq mi (11.499/km2)
Time zoneUTC−6 (Central)
 • Summer (DST)UTC−5 (CDT)
Area code712
Congressional district4th
Websiteplymouthcountyiowa.gov
  • Iowa county number 75

Plymouth County is the westernmost county in the U.S. state of Iowa. As of the 2020 census, the population was 25,698, and was estimated to be 25,825 in 2024. The county seat and the largest city is Le Mars. Plymouth County was named after Plymouth, Massachusetts.

Plymouth County is part of the Sioux City, IA-NE-SD Metropolitan Statistical Area.