If, instead of building a dam, they had used that concrete to build a road, it would have been a two-lane highway stretching from San Francisco to New York.

If, instead of building a dam, they had built a skyscraper, it would have been 60 stories high. If they had built an Egyptian pyramid, there would be stuff left over.

These are some of the amazing facts you will learn right off if you visit Hoover Dam. Everyone is impressed with the size and scope of the thing — and rightly so.

When it was built in the early 1930s, nothing on this scale had been attempted before. When it was finished, it was the highest dam in the world.

Who cares if it has now fallen out of the Top 10 worldwide and is only the third-highest dam in the United States. Those statistics are still impressive. As are these:

Hoover Dam is 726.4 feet high, 45 feet thick at the top, 600 feet thick at the bottom and 1,244 feet across the top. Lake Mead, which was created by the dam, is still the country's largest man-made reservoir. When full, it is 110-115 miles long, with 550 miles of shoreline and a water capacity of about 32 million acre feet — or enough to cover the state of Pennsylvania to a depth of one foot.

As you look at the dam, it is fun to ooh-and-awe over these numbers.

Less obvious visually, but of greater importance economically, is the role Hoover Dam has played — and continues to play — in the West.

If there were no Hoover Dam, there would be no Las Vegas, no Los Angeles — or, at least very different ones. Urban development, agriculture and recreation would not be the same.

You learn many other things at the dam's visitors center, as well. For example, more than one million acres of America's richest crop lands — producing fruits, vegetables, cotton and hay — are irrigated by water made available by Hoover Dam. You learn that more than 18 million people in Las Vegas, Los Angeles, San Diego, Phoenix, Tucson and other southwestern cities and towns have their domestic water needs supplied by the dam.

And, the electricity generated by the hydro-electric power plant — more than 4 billion kilowatt hours a year — serves 1.3 million people in Nevada, Arizona and California. (About 25 percent of the power goes to Nevada, 19 percent to Arizona and the rest to California.)