Here is a close up of the trunk and crack

Best advice, take it out and replace it with something you know and want; John's first rule of trees... you are going to live a lot of years with this ttee; you are going to put a lot of energy, money, time, fertilizer, water; so you should begin with the biggest, best, tree that you can find/afford. It is like buttoning your shirt... if you get the first button wrong, it doesn't matter how careful you are after that.

Yeah, I figured that's the easiest option. Was still hoping someone might have some insight onto what may have caused this though. I really wouldn't want to take it out, plant a new one, and have the new tree die from the same issue if it is something in my yard that may have caused this tree to die.

Having the tree in the lawn, particularly with lawn right up to the trunk pretty much guarantees the death of a citrus tree. Sometimes it will take some time to succumb.

I'm guessing the lawn is watered by sprinklers and those sprinklers were hitting the trunk of the tree. That can be very bad also. Sometimes it will take some time to succumb.

That one is done. If you want to plant others, they must go where there is no lawn and no sprinklers hitting the trunk.

Thanks for the response. I had wondered if it had something to do with the watering. Sad that it will have to come out. I don't think we will be replacing it with another citrus tree.

Yes, looks like crown rot. When you replant make sure the crown is set above grade about 1.5" and will not settle when the nursery potting mix is eaten away by the soil bacteria. Other posted (excellent) suggestions also apply.

Awww, too bad. looks like it was a beautiful tree. Buy a new one.