I can't seem to post pics, so I'll try describing the problem for now, and try to post the photos again later.

My locust was a well-matured tree when I moved in 6 years ago. Last year, a couple of small, lower branches died off over winter; nothing major.

This spring, the tree still is not completely leafed out. It looks sparse with more small dead branches throughout. From top to bottom, this tree has sections where the ends of the branches still have no leaves, giving it a patchy appearance.

Just to the east of it (maybe 50 or 60 feet) sits a large silver maple. The two tree canopies are nearly touching. I wonder if the silver maple is crowding out the locust?

My neighbor thinks both trees were planted in 1970 or 1971, to give you an idea on the age.

I LOVE this tree. I have done some research, and I don't see any obvious cankers.

Any idea without photos of what could be happening?