Paul Tracy

On Dec. 20, 1922, a surveyor -- J.G. Tierney -- made his way along the Colorado River by barge. Tierney, who worked for the U.S. government, was surveying a remote spot in the Mojave Desert called Boulder Canyon.

Boulder Canyon sits in the middle of some of the most unforgiving land in America.

During the summer, temperatures frequently top out near 120 degrees. Less than five inches of rain fall each year. Rattlesnakes and scorpions hide under rocks. And the sharp cliffs are near-impossible to scale.

And yet, this canyon in the heart of the desert holds one of the greatest investments in U.S. history... one that has generated billions of dollars in wealth and is practically guaranteed to keep doing so for decades.

But it wasn't without its costs. In total, 112 men -- beginning with J.G. Tierney, who on that December day drowned after falling off the barge that carried him and his equipment -- died to create this investment.

I'm talking about Hoover Dam.

Before I get too far... no, I am not recommending that you invest in the Hoover Dam. Even if you wanted to, it's fully owned by the U.S. government. There's not a stock you can buy that gives you access.

Instead, it's what Hoover Dam represents that is the true opportunity to grow your wealth.

Let me explain...

Hoover Dam (originally called Boulder Dam) was finished in 1936, at which point it began damming the Colorado River to create Lake Mead -- the United States' largest reservoir.

The project was massive. At its peak, more than 5,000 people worked on it at the same time. And the dam contains enough concrete to pave a two-lane highway from San Francisco to New York City.

In total, construction costs came to $49 million.

That $49 million investment is the sole reason why millions of people are able to live in the Las Vegas area today. And it has generated billions of dollars of wealth in the process.

But Hoover Dam didn't just create a massive reservoir to provide water to the middle of the desert. It also created one of the most lucrative electricity generation plants ever built.

Located in the base of the dam are 17 hydroelectric turbines that make up the Hoover Powerplant. These turbines generate roughly 4.2 billion kilowatt hours (kWh) of electricity per year, making it one of the largest hydroelectric plants in the United States.