By late afternoon at Cowan Lake State Park the reservoir is full of sails, small boats tacking back and forth across the open water south of Dayton while the campground loop stays in the shade of the trees along the shore. It's a lake for staying put. The rig sits under the canopy all week, and each day ends when the last boats come in off the water.
Cowan's spot between Dayton and Cincinnati helps on a longer stay. If you tow a trailer or bring a car along, a rainy day can go to a museum in either city while the site stays set up and the awning stays out.
Reserve the campsite before you choose the rig. The length and hookups listed for the exact site you land on decide the rental, whether that's a shorter Class C, a longer motorhome, or a towable an owner drops on the pad.
If the site comes up short or it's just the two of you, Caesar Creek and its gorge, along with the walks at John Bryan State Park and Clifton Gorge, are the smaller-rig trips on the Dayton campervan page. That page also covers the National Museum of the U.S. Air Force, with its hangars of aircraft, and the weekend run north to Indian Lake.
Hamvention week at the Greene County Expo Center, Xenia
In mid-May, Hamvention brings the amateur radio world to the Greene County Expo Center in Xenia, and for a lot of the people who come, the campground is half the show. Rigs park in rows with antenna masts raised beside them, the flea market spreads across the fairgrounds in tables of radio gear, and the walk from your door to the swap tables is short enough to make three trips before lunch.
The Hamvention camping has water and electric at the site, with 30 or 50 amp service in limited supply, and it doesn't allow tents or sleeping in a personal vehicle, so a motorhome or a towable is how you stay. With no sewer at the site, arrive with empty tanks and plan to dump on the way out at one of the grounds' two dump stations.
Hamvention is the spike in the Dayton rental calendar. The hams and the families planning a mid-May week at Cowan Lake are renting from the same owners, so lock the Expo camping spot before the rig, and if the lake is your plan, either pick a different week or book both early.
Grand Lake St. Marys and the long open water
Out at Grand Lake St. Marys the water goes wide and shallow, running to a flat horizon where the far shore is barely a line. It suits a family that wants a bigger lake for the parked week, with evenings at the shoreline watching the light go across all that open water.
The order is the same as at Cowan: reserve the state park site, then rent to the length listed for it. The rest of the state's RV lakes, the Lake Erie shore included, are on the Ohio RV page.
For a close-in first night before either lake, Dayton KOA Holiday in Brookville sits off I-70 at Exit 24 with full RV hookups, so you can start the week with fresh water topped up and tanks empty. The kids get paddle boats beside the pads and a pool open Memorial Day to Labor Day.
