A renewed effort to see what's lurking at the bottom of Lake Minnetonka has uncovered three historically significant shipwrecks from when the lake was a popular tourist attraction at the turn of the 20th century.

Tempted to don a diving suit and seek out a treasure chest?

You'd come up empty-handed, because these wrecks and others, mostly steamboats, ferries or barges, were stripped clean of anything valuable and some were intentionally sunk when they became outdated.

"Artifacts for us are the fittings on the boats, the different cleats, the wheels if they're left on," said Ann Merriman of Maritime Heritage Minnesota, which found the remains during a sonar survey that also turned up several dozen smaller images that may be rowboats, cars or other long-lost items.

Seeing how the boats were crafted and used is historically important and their locations will be mapped so that they can be recognized as state archaeological sites. That would help keep them safe from disruption and allow divers to explore their wreckage.

"Our goal is to keep wrecks safe from looting, and safe from damage from anchors, but it's certainly not to limit scuba divers' enjoyment of them," Merriman said.

Merriman and her husband, Chris Olson, trolled the eastern, or lower half, of the large lake last fall and took hundreds of sonar images. The couple will survey the other half of Lake Minnetonka next month, looking for more.

Tourism mecca

Six other wrecks are already widely known in the lake, five of them on the north side of Big Island, where a large amusement park drew tens of thousands of tourists in the early 1900s. Many were Twin Cities residents who took streetcars to the lake, then rode steamboats to the island and other popular spots.

Many of those boats were neglected at the end of their working lives, and then scuttled to get rid of them, said Scott Anfinson, Minnesota state archaeologist.

In the mid-1990s, the state archaeology office hired divers to look at suspected areas for shipwrecks in Minnetonka, the Mississippi River and Lake Superior, and some sites were identified.

State law dictates that all shipwrecks and other historic and archaeological sites on public property should be protected.

However, the latest sonar work by Merriman and Olson is the first systematic look at the bottom of Minnetonka, Anfinson said, and the team is using better technology to sleuth for discoveries.

"When you put archaeology and underwater work together and have shipwrecks, that's a National Geographic story right there," he said.

The new wrecks were found in St. Albans Bay, Wayzata Bay and northeast of Big Island. The Wayzata Bay wreck is about 70 feet long and 20 feet wide, sitting in about 40 feet of water. It was likely a steamboat. The vessel in St. Albans Bay, also 40 feet underwater, is slightly shorter and wider, and appears to be a barge that may have been built around 1925.

The wreck northeast of Big Island is about 60 feet deep, and is probably a 50-foot steam or gasoline-powered launch from the late 1800s.

More sleuthing ahead

Merriman and Olson plan to survey the other half of Lake Minnetonka next month. Last fall's field work was funded with private donations and a $7,000 grant from the Arts and Cultural Heritage Fund that's part of the Clean Water, Land and Legacy Amendment. Another $7,000 Legacy grant has been awarded for this year's survey. The recipient is the nonprofit Maritime Heritage Minnesota, which Merriman and Olson founded in 2005. It has searched several other Minnesota lakes and rivers.

Merriman said the survey work is like "mowing the lawn," using a GPS to move slowly back and forth across the lake, bouncing waves off its bottom to look at images. In addition to the three new wrecks, the couple found 75 "anomalies" that look like human-made objects. They include what could be rowboats, sailboats, cars, fish houses and other unknown items. Some of the objects may just be piles of rocks, she said.

In addition to boats that were intentionally sunk, there are historic records of other boats whose boilers exploded, and sailboats or smaller craft that capsized, sank and have never been recovered.

"We're fairly confident that at least nine of the anomalies are smaller wrecks, but we'd have to get on our scuba gear and look at them at close-range to know for sure," Merriman said.

After analyzing this year's images, she said, the couple would like to begin diving to get a closer look at the various objects. That effort would cost at least $50,000, she said, and would take one or two summers to complete.

Transit by lake

Anfinson said the discoveries illustrate how important steamboats were in state history, and in the post-Civil War settlement of the Lake Minnetonka area in particular.

"You look at the pictures of the Excelsior wharf or the Wayzata wharf, and you see steamboats there that could carry 1,000 people," he said. Excursion boats that toured the lake through the late 1800s served food and provided music. The scale of tourism shrunk after the 1893 economic crash, but smaller charters continued to serve tourists. By 1906 the Twin City Rapid Transit Co. had extended its streetcar lines to the Minnetonka area, and built several "streetcar boats" to ferry riders to destinations around the lake. Few people had cars, and roads and bridges weren't fully developed, Anfinson said, but people wanted to move around.

Merriman said the transit company designed its boats to look like floating streetcars. "They even had the same color and wicker seats," she said. "You get off a streetcar and get onto a streetcar boat. It was a great marketing tool."

Tom Meersman • 612-673-7388