When I cleared out a seedling bed, I left this "tree" that had come up in the middle. I suppose it could be a shrubby bush that just developed into a standard.

There are thorns on the trunk and branches. do you think it's a Locust tree?

It could possibly be this one http://www.wildflower.org/plan...

It does look like a black locust, Robinia pseodoacacia. Does it have paired thorns at the nodes as suggested in this ID page?:

https://www.uwgb.edu/biodivers...

I think everyone is right and it's a Black Locust .................

I think it's out of here .... maybe I'll see if I can find a marked down Japanese Maple for that spot.

Warning: This species naturalizes easily and is considered an invasive weed in many of its non-native areas of establishment. Its brittle branches (subject to breaking in winds), vicious thorns, rampant root sprouts and copious seeding make this species a garden thug.

I planted a Black Locust once and I loved the looks of the foliage, but the thorns on the trunk became a big problem, I even tried cutting them off but they grew back, so sadly the tree had to go.

I agree, it sure looks like Black Locust (Robinia pseudoacacia)
http://www.michigan.gov/docume...
https://en.wikipedia.org/wiki/...