The company I work for has a mandatory business trip in another state.
The non exempt empoyees only get their 8 hr day wages paid, all the other time we spend their is unpaid.
Is this legal?

Are you actually going to be working more than 8 hours in a day? If evenings are on your own, that time need not be paid.

And, how are you travelling there and when?

Fly On Plane , Everyday Is More Than 8 Hrs Some Are 14 Hr Days

If your flight coincides with your regularly scheduled work hours, even if it's on a day when you aren't normally scheduled to work, that time must be paid. If not, then it doesn't. The law also does not require pay during nonscheduled work hours for commute time to the airport and airport waiting time.

http://www.dol.gov/dol/allcfr/ESA/Title_29/Part_785/29CFR785.39.htm