Hamlin County is a county in South Dakota, United States, in the northeastern part of the state, roughly midway between Watertown and Brookings. It had a population of 6,164 at the 2020 census and covers 507 square miles (1,310 km2) of land plus 31 square miles (80 km2) of water, centred near 44°41′N 97°12′W.
Hayti is the county seat, and its postal code is 57241. The county has four cities, two towns, and three unincorporated communities, no CDPs, and is divided into thirteen civil townships. It sits in the Central time zone.
Towns & Villages in Hamlin County
Hamlin County’s nine named places break down as four incorporated cities, two incorporated towns, and three unincorporated communities (marked Unincorp. below). Populations are shown where individually verified; otherwise the cell reads —.
| Place | Type | Township | Pop. | ZIP |
|---|---|---|---|---|
| Hayti | City · seat | Hayti | — | 57241 |
| Bryant | City | — | — | 57221 |
| Castlewood | City | Castlewood | — | 57223 |
| Estelline | City | Estelline | — | 57234 |
| Lake Norden | City | Norden | — | 57248 |
| Hazel | Town | — | — | 57242 |
| Baxter Slough | Unincorp. | — | — | — |
| Dempster | Unincorp. | Dempster | — | — |
| Thomas | Unincorp. | — | — | — |
Estelline is the largest incorporated place in the county. A handful of names that circulated on older place lists for Hamlin County — including “Claremont Colony,” “Kones Corner,” “Poinsett Colony,” and “Stone Bridge” — are Hutterite colonies or informal rural landmarks rather than incorporated or census-recognized communities and are omitted here for lack of independent verification; see notes.md.
ZIP Codes
- 57221 — Bryant
- 57223 — Castlewood
- 57234 — Estelline
- 57241 — Hayti (post office town)
- 57242 — Hazel
- 57248 — Lake Norden
Six ZIP codes serve Hamlin County; smaller unincorporated communities such as Baxter Slough, Dempster, and Thomas draw mail service from the nearest of these post offices rather than carrying a ZIP of their own.
Geography
Hamlin County is made up of low, rolling hills dotted with small lakes and ponds, with most of the land given over to farming. The terrain slopes toward the south-southeast; its highest point, 1,949 feet (594 m) above sea level, sits on the eastern boundary near the northeast corner. Lake Poinsett and Lake Norden are the county’s best-known water bodies, both popular for walleye and perch fishing.
Hamlin County borders Codington County to the north, Deuel County to the east, Brookings County to the southeast, Kingsbury County to the southwest, and Clark County to the west. Of these, Deuel County and Clark County have their own Towns & Villages profiles on this site.
Demographics
The 2020 census counted 6,164 residents in Hamlin County. Estelline and Castlewood are its two largest incorporated communities. Median household income across South Dakota stood at the state median of $71,810 (2023 ACS); county-level income for Hamlin County is not independently verified here. With 507 square miles of land, the county’s population density works out to roughly 12 people per square mile, well below the statewide average and typical of the northeastern plains.
Economy & Local Life
Agriculture drives Hamlin County’s economy, with corn, soybeans, and small grains grown across the rolling farmland and cattle raised on the lower, wetter ground near its lakes. Lake Poinsett and Lake Norden support a seasonal tourism trade of anglers and cabin owners drawn from Watertown, Brookings, and Sioux Falls. Hayti and Estelline serve as the county’s retail and grain-elevator hubs.
History
Hamlin County was created by the Dakota Territorial legislature in 1873 and organized in 1878. It was named for Hannibal Hamlin, who served as vice president under Abraham Lincoln during Lincoln’s first term. Early settlement clustered around the county’s lakes and along the railroad lines that later became the towns of Hayti, Estelline, Castlewood, and Bryant.
Getting There
Interstate 29 runs along the county’s eastern edge, and U.S. Route 81 crosses the county north–south through Bryant and Castlewood; South Dakota Highways 21, 22, and 28 provide the main east–west connections.
- Watertown — about 20 miles north
- Brookings — about 30 miles south
- Sioux Falls — about 90 miles south
Watertown Regional Airport, roughly 20 miles north of Hayti, is the nearest commercial airport; Sioux Falls Regional Airport, about 90 miles south, offers a wider range of flights.
Frequently Asked Questions
Where is Hamlin County, South Dakota?
It sits in the northeastern part of the state, between Watertown and Brookings, bordered by Codington, Deuel, Brookings, Kingsbury, and Clark counties.
What is the population of Hamlin County?
6,164 people, per the 2020 census.
How big is Hamlin County?
507 square miles (1,310 km2) of land plus 31 square miles (80 km2) of water, for a total of 538 square miles.
What is the county seat of Hamlin County?
Hayti is the county seat.
How many towns and cities are in Hamlin County?
Four cities (Bryant, Castlewood, Estelline, Lake Norden), two towns (Hayti, Hazel), and three unincorporated communities (Baxter Slough, Dempster, Thomas).
What ZIP codes are in Hamlin County?
57221, 57223, 57234, 57241, 57242, and 57248.
What is Hamlin County named after?
Hannibal Hamlin, Abraham Lincoln’s first vice president.
More counties in this state: Towns and villages in South Dakota.