LAKE OZARK, MO. ? At a time when the nation’s economic fortunes plummeted to disastrous depths, a manmade marvel arose from the forests and fertile farmland along the Osage River basin.

Modern-day tourists flock to Lake of the Ozarks for its miles of shoreline, weekend getaway homes and hidden fishing coves. But to folks living in the hard-luck Great Depression years, the dam that created the contemporary recreational paradise was the real attraction.

Public access to Bagnell Dam has been off-limits for the past decade, after dam owner AmerenUE discontinued regular tours because of safety and liability concerns. But this weekend, the dam is back on display as part of its 75th anniversary.

The project relied on the sweat of 20,000 men – up to 5,000 at any given time – working around the clock to clear brush, dig ditches, haul steel, excavate bedrock and ultimately erect the 146-foot tall dam, using horses and steam shovels rather than heavy machinery.

The pay was 35 cents a day, but work was work.

“They did this in 18 months,” said plant manager Warren Witt. “It takes most people now 18 months to build a house.”

Dam construction by Union Electric Co. of St. Louis, the forerunner to AmerenUE, began on Aug. 6, 1929, two months before the Wall Street stock market crash.

By May 30, 1931, cars were traveling over the dam. Commercial operations began less than five months later at what then was the nation’s largest manmade lake.

Sixth-grade students from School of the Osage Upper Elementary try to identify fish swimming Friday near the Bagnell Dam, in Lake Ozark, Mo. AmerenUE has opened the dam for public tours this weekend to mark the structure's 75th anniversary.

The dam’s value as a tourist attraction soon was eclipsed by the lake itself, although before ending tours 10 years ago the structure continued to draw 35,000 visitors annually, AmerenUE officials said.

Still, many lake visitors take little time to ponder the true purpose of the dam, which holds back 600 billion gallons of water and at one time generated one-third of Missouri’s electricity. These days, that contribution has declined to 1 percent.

“The huge tourism industry that’s grown here has in the minds of many overshadowed the real purpose of Bagnell Dam, which is to generate electricity,” said Alan Sullivan, an AmerenUE consulting engineer.

Among the dam workers was Lloyd Slone, Sullivan’s uncle. Now 93, Slone was one of the dignitaries at a Friday afternoon commemoration ceremony.

Earlier Friday, busloads of local school children joined weekend visitors to explore the dam’s inner workings, walking past gargantuan turbines, generators and coils of elevated transformers while peering through a fence that overlooked the dozen spillways that control water flow.

The students at times seemed more interested in each other’s clothing than the intricacies of hydroelectric power, but tour guides like Kenny Runge hoped the up-close view would offer at least some insight into a modern necessity most take for granted.

“All you know is that you turn a light on in your house and it comes on,” said Runge, a hydroelectric maintenance technician. “They don’t have any idea how it’s produced.”