If you were standing next to the likes of Yao Ming, Shawn Bradley or Shaquille O'Neal, you'd probably seem pretty short.

In similar fashion, Kennecott Copper's Garfield Smelter smokestack is dwarfed as it stands adjacent to the 9,000-plus-foot Oquirrh Mountains, which rise more than 4,000 feet above the Salt Lake Valley.

However, the reality is that the Kennecott smokestack is one of the loftiest, free-standing structures in the world and the tallest such thing west of the Mississippi.

Rising sharply about a dozen miles west of Salt Lake City and just south of I-80, this icon, which turns 35 this fall, is by far the tallest man-made structure in Utah at 1,215 feet.

It's almost the equivalent of having an Empire State Building high structure rising up, or equal to the height of three LDS Church Office Buildings (state's runner-up highest free-standing structure).

Built in 1974, the smokestack's hexagon-shaped base is 177 feet across.

You really don't want to stand right next to Kennecott Copper's Garfield smelter smokestack either. That's because you'll almost crack your neck, straining to look straight up and see the seemingly endless top of this mammoth structure.

A look inside its base reveals a surprising amount of open space, surrounded by concrete up to 12 feet thick.

The concrete itself towers to an even 1,200 feet, and then the fiberglass flue goes up another 15 feet.

"It's overkill for this (refinery) plant," said Jack Haymond, a consulting engineer for Kennecott who has worked there for 45 years. "But it was here. … It would cost a fortune to take it down."

He said when the federal Clean Air Act came along in 1970, Kennecott built the stack, which at the time was a good fit. It was just high enough to disperse waste gases, according to the new standards. However, with leaping advances in pollution controls, it is now taller than it needs to be.

Haymond said Kennecott, owned by Rio Tinto, is one of the two cleanest smelters in the world, capturing 99.9 percent of all the sulphur gas released.

The chimney replaced several predecessor Kennecott smokestacks, now demolished, the tallest of which was a height of 413 feet.

"They commandeered every cement truck in northern Utah" when they built it, Haymond said. Concrete flowed — more than 26,000 cubic yards — for 84 days, 24/7, minus one short break, to complete it. Some 900 tons of steel were also required.

Work on the stack began on Aug. 26, 1974, and was finished in less than three months. It is built according to Zone 3 seismic standards.

It cost $16.3 million at the time to build, the rough equivalent of almost $70 million in today's dollars.