Rock Island: least-visited state park in Wis.

The handwritten sign says “Rock Island Café,” and the only thing on the menu is fresh berries during this time of year. The sequence begins with strawberries in early July, then raspberries and thimbleberries. As summer inches into fall, blackberries ripen.

You won’t see an actual restaurant, and berries are free for the taking, but you have to work for them. They grow wild within the 912 acres of Rock Island State Park; a park volunteer likely can show you where.

Rock Island holds the distinction of being the least-visited state park in Wisconsin, but it’s not for lack of luster. It’s for lack of easy access. Getting to the island requires a half-hour ferry ride from the tip of the Door County mainland to Washington Island, then a short drive, then a 15-minute ride on another ferry.

The first ferry operates all year, weather permitting, and crosses the sometimes-turbulent Death’s Door passageway between Green Bay and Lake Michigan. The shorter ride comes on a smaller boat that sails at least three times daily from Memorial Day weekend through Columbus Day.

Rock Island State Park recorded 16,179 visitors in 2006, the most recent year for which statewide attendance records are available. Peak attendance was 16,998 visitors in 2000. (Wisconsin’s most-visited state park is Devil’s Lake, with 1.1 million visitors annually.)

Since it’s unusually remote, the 40 rustic campsites on Rock Island can be reserved. Expect outhouses, no showers, no hook-ups for electricity. You can buy firewood but not ice. Pump water from a well, and bring containers big enough to carry it to your campsite.

Boaters who choose to moor overnight pay $1 per foot of boat length, but the water’s mood swings make boating unpredictable and sometimes dangerous. Not a good match for a lightweight vessel or novice navigator.

Island exploration takes place on foot, by hiking the six-mile perimeter, plus about four miles of crisscross trails that tend to be wide, well-maintained and often shaded. Cars and bicycles are not allowed.

What is there to see? Bursts of color from wildflowers, a splendid sand beach, dolomite cliffs and see-the-bottom water are fine selling points – yet not unusual among Wisconsin parks.

One standout attraction is Potawatomi Light, the state’s oldest and up since 1836; take off your shoes before touring this tidy little lighthouse. The view from the top will take you 20 miles away on a clear day.

An old stone water tower has been on the National Register of Historic Places since 1985. So have other quaint cobbled buildings, including the Boat House and its enormous Viking Hall, whose exhibits explain the park’s history.

A wealthy Chicago man, Chester Thordarson, made his money from high voltage electrical inventions and bought Rock Island for $5,735 in 1910. He turned it into a summer estate and filled it with reminders of Icelandic and Scandinavian heritage: Elaborate hand-carved oak furniture still graces the library – and a looming fireplace will be among the widest and tallest you’ve seen.

In winter, when ice freezes between Washington and Rock, adventurous ice fishermen and cross country skiers trek the 1.25 miles between islands. They don’t get the park’s blessing.

“We don’t encourage people to venture onto the ice, but they do anyway,” says Randy Holm, park ranger. From his perspective, Rock Island “has been discovered – we have a lot of visitors.”

“You have to know what you’re doing,” Kirby Foss, park manager since 1999, says of the winter explorers. The park office moves to Jackson Harbor, on Washington Island, after Columbus Day, so Rock Island remains unstaffed in winter.

“Dealing with the weather, especially the northwest winds” is Kirby’s biggest work challenge, but “we have a good operation” that is enhanced by Friends of Rock Island, volunteers who are passionate and active about park operations.

Mid summer is the park’s busiest time, but he considers early fall another good time to visit. “We have cold, wet springs, but Lake Michigan returns its favor in September and October, when it’s warmer here than in Green Bay.”

Least visited? That was news to the park crew, but not unwelcome. Having room to roam without human congestion, they agree, is not necessarily a bad thing.

For more about Rock Island State Park: www.dnr.state.wi.us, 920-847-2235.

The 15-minute ferry ride costs $9 roundtrip (campers get a discount; $5 for riders age 5-10). For more about the Rock Island Ferry: 920-847-3322.

For more about the Friends of Rock Island, whose volunteers help visitors, lead lighthouse tours and assist with park maintenance: www.uniontel.net/~cmarlspc.