Before there were people, Lake Bonneville covered a good part of Utah, as well as parts of Idaho and Nevada. Then it shrank down to what is today the Great Salt Lake, which is less salty than the Dead Sea, but pretty much saltier than anything else. To the east is the Wasatch front of the Rocky Mountains, and to the west is...well, lots of nothing. Salt flats. If you drive I-80, you will see miles and miles and MILES of this. It's really quite amazing. (Please pull over and rest if it is too hypnotic, however.)
In 1849, Mormon settlers fleeing mob persecution in Illinois chose the Salt Lake valley to settle in. They figured no one else would want to live there, as it was pretty much barren and isolated. But they made it grow, and now it's basically huge. It's home to the University of Utah, as well as of course the worldwide headquarters of the Church of Jesus Christ of Latter-day Saints.
Some things you might see in Salt Lake:
The LDS conference center:
The Salt Lake temple, which took 40 years to build.
Only members in good standing can enter, as it's considered a holy place, but there is a very nice visitor's center, and anyone (LDS or not) is welcome there and on the temple grounds. There is a facsimile of the famous Danish Christus statue in the visitor's center.
There are a lot of interesting, historic homes downtown, like this one (which I believe is a reception center now?)
The freeways have expanded considerably in the past twenty years, so that now they are starting to remind me of Los Angeles. At least, they have that many lanes nowadays, especially as all cities are lined up more or less along I-15/the Wasatch front. Here are some things you can see outside your window as you cruise up the freeway: