Old Mill State Park

This guide is for campers and day visitors in the Red River Valley and for anyone planning around the mill's once-a-year Grinding Day. It covers the campground, trails, the mill, seasons, fees and directions. Facts come from the Minnesota DNR park page, the DNR park map and the DNR fee and reservation pages, listed at the end.

The park in brief

The DNR describes the park as "like an island of original landscape in a sea of crop land," with riverine forest, small patches of oak savanna and prairie on old beach ridges, and wet prairie in the low areas. The DNR explains that the ridges are old shorelines of a vast freshwater lake that once covered the northwest corner of the state.

The site was homesteaded by the Larson family in 1882, and a series of mills was built here starting in 1886. The DNR history says the first mill was water powered, was rebuilt in 1889 as a wind-powered mill after floods, and that John Larson, the homesteader's son, later ran a mill powered by a Case steam engine. The mills were moved to the current site in 1897. For 1937, the two DNR sources word it differently: the park page says the mills were owned and operated by several people before being "sold to the state in 1937," while the park map says the steam mill "remained in operation until 1937." The engine and mill were rebuilt in 1958.

Staffing note: the DNR says the Old Mill office "is no longer staffed." Register campsites by phone or online, and buy vehicle permits or firewood with the self-service QR codes outside the office building, or buy your permit online before you arrive. The DNR adds that the Old Mill email is not checked every day, so contact Lake Bronson State Park for faster answers.

Camping at Old Mill

The campground holds 25 mostly shaded sites near the Middle River, within easy walking distance of the Larson Mill, according to the DNR.

Season: the DNR says the campground is open Memorial weekend through MEA weekend in mid-October. As of November 2026, camping is closed for the season.

Reservations: book online at the DNR reservation site or call 866-857-2757. The DNR reservation FAQ says every state park campsite needs a reservation, bookings open up to 120 days before arrival, and on the first day a date opens, online booking starts at 8 a.m. Central. Same-day reservations carry no reservation fee. See the state park reservations guide for how the system works.

The mill, trails and swimming

Larson Mill and Grinding Day

The DNR lists the Larson Mill, a Pioneer Cabin and WPA-era structures as historic sites in the park. The park page says the steam engine and mill "are fired up each year" for special events, and that Grinding Day is held on the last Sunday of August before Labor Day weekend, when the Marshall County Historical Society runs the steam engine and grist mill. The park map words the timing as "the end of August." The park has no seasonal naturalist; the Friends of Old Mill State Park sponsor occasional programs.

The DNR history also notes that the Pembina Trail, an oxcart route along the beach ridge just east of the park, and its river crossing "are still visible."

Trails

The DNR feed lists 7 miles of hiking trail, a mile of self-guided trail and a mile of horse trail that connects to trails outside the park. The park map names three trails:

Note that the feed calls the self-guided trail "a mile," while the map gives the Agassiz Self-Guided Trail as a 1.3-mile loop. For a short visit, the map suggests the Larson Mill and Pioneer Cabin, the Stone Bridge, and the Agassiz trail for prairie flowers.

Swimming, picnics and wildlife

The swimming pond is open Memorial weekend through Labor Day weekend, and no watercraft are allowed in it. The park also has a picnic area, a playground and an enclosed picnic shelter that can be rented in summer through Lake Bronson State Park. A walking bridge near the campground is closed to motorized vehicles.

For wildlife, the DNR mentions deer, beaver, ruffed grouse, white-tailed jackrabbit and snowshoe hare, with warblers and finches abundant during spring and fall migration. The park page says "about 100 species of birds reside in the park"; the park map says to watch for "over 100 bird species."

When to go

Late May to mid-October is the main season: the campground runs Memorial weekend through MEA weekend, the swimming pond Memorial weekend through Labor Day weekend, and Grinding Day falls at the end of August. As of November 2026, the DNR reports:

• Camping is closed for the season (alert updated November 3, 2026).
• Campground water is off for the 2026 season, though a separate DNR note says drinking water is available year-round behind the park office.
• Vault toilets stay open year-round.

The alert also listed a firearms deer hunt November 7 to 10, 2026, with blaze orange recommended for visitors on those days.

Winter: the park has 1.5 miles of groomed snowmobile trail and a sliding hill, and snowshoeing is allowed anywhere except on groomed snowmobile trails. The DNR notes the warming house is not plowed in winter. Horses may use designated snowmobile trails between March 16 and November 30.

Fees and permits

From the DNR vehicle permit page and fee schedule, before tax. The fee schedule gives statewide ranges; ReserveMN shows the exact price of each Old Mill site.

Two nights at an electric site, worked from the DNR fee ranges: 2 × ($20 + $10) + $8 = $68 at the low end, or 2 × ($35 + $10) + $8 = $98 at the high end, plus a vehicle permit ($7 overnight or $35 year-round). For multi-night stays, ask the park which permit covers your whole stay; the year-round permit covers every visit for a year.

The DNR says to buy firewood at the park (the ranger station, or the self-service QR codes while the office is unstaffed) or through Yodel; the park map also allows wood from vendors approved for this park. Gathering firewood in state parks is not allowed.

Getting there

The DNR directions, quoted as written (the Argyle leg is worded ambiguously, so confirm your route on a map): "From Newfolden, go 11 miles west on County Road 4. From Argyle, go 12 miles east on County Road 4, then 1 mile north on County Road 4 to County Road 39." The DNR lists Argyle and New Folden as the nearest towns. Lake Bronson State Park, which manages Old Mill, is the contact for questions.

For other parks in the region, see the northwest Minnesota guides, including the Lake Bronson State Park guide, the Hayes Lake State Park guide and the Buffalo River State Park guide, or search the park finder.

Before you go

1. Buy your vehicle permit online before you leave; the office is not staffed.
2. Reserve your campsite online or by phone, even for a same-day stay.
3. Fill RV water and empty tanks before arriving; the nearest dump station is in Warren.
4. Check the Grinding Day date with Lake Bronson State Park if you want to see the mill run.
5. Bring approved firewood or plan to buy it on site.
6. Call Lake Bronson State Park (218-754-2200) with questions rather than emailing Old Mill.

Related guides: Lake Bronson State Park · Hayes Lake State Park · Buffalo River State Park · All northwest Minnesota guides

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Sources

• Minnesota DNR, Old Mill State Park (camping, trails, history, seasonal update, alerts): https://www.dnr.state.mn.us/state-parks/park.html?id=spk00247
• Minnesota DNR, Old Mill State Park map and guide (PDF, 2025): https://files.dnr.state.mn.us/maps/state_parks/spk00247.pdf
• Minnesota DNR, Reservation FAQ: https://www.dnr.state.mn.us/reserve-faq/index.html
• Minnesota DNR, State park fees: https://www.dnr.state.mn.us/state_parks/fees.html
• Minnesota DNR, Vehicle permits: https://www.dnr.state.mn.us/state-parks/permit.html