I have a locust tree that has been having branches die off and now the crown? center part died off this year.  I heard when the crown dies the tree is on its way out.  Is there anything I can do to resurrect the tree?  If not, what signs do I look for to know when to take it down so it doesn't fall on a house / fence?

On a separate note, there is another tree growing near the base of the locust tree.  Do you know what kind of tree this is and whether the tree is appropriate for Northern Colorado?

Thanks!