The next time you see a train rolling down the tracks, ask yourself, "How much does that locomotive weigh?" You'd be in the ballpark if your guess is around 400,000 to 500,000 pounds.

Can you imagine one tipping the scales at over one million pounds? That would be 'Big Boy,' Union Pacific's goliath of all locomotives, and it will embark on a nationwide tour this summer.

Is Big Boy Coming To South Dakota?

The first leg of the Big Boy No. 4014 Westbound Tour takes this railroad legend west from Wyoming through Utah, Nevada, California, and Idaho.

If you want to get an up-close view of Big Boy you'll be able to catch up with the Heartland of America Tour after August 29 when it leaves Cheyenne, Wyoming on an 8-week tour through Arkansas, Colorado, Illinois, Iowa, Kansas, Missouri, Nebraska, Oklahoma and Texas.

How Big Is 'Big Boy'?

Introduced in 1941, Big Boy 4014 weighs 1.2 million pounds and is 132 feet long. A normal diesel locomotive is about half that size.

According to Union Pacific officials, some scheduled stops will be brief. Otherwise known as "whistle stops."