This Agave was given to me some time ago as young pup, it is now big and beautiful, but I still don't know it's name, I hope someone can help.
It is yellow green and winter hardy.

It looks like Agave desmetiana to me. It's hardy to 25F but of course sometimes the information is wrong on that.

Thank you Dee, very kind of you to answer my question, I will check out Agave desmetiana.

I have looked and Agave desmetiana matches mine in color and form, but the edges are smooth while mine has
spines along the edges.
Could this be a green form of Agave americana? It looks just like it except for the color.

There are versions of A. desmettiana that have teeth, but that said, the leaves and the openness of the rosette look wrong for Agave desmettiana, as does the terminal spine, which are not that gigantic in A. desmettianas I have seen.

I do not have a real good alternative ID to suggest, one guess: it could be a really floppy A. salmiana, how much sun does it get?

It gets about half day of sun, thank you for your response.

I sure would like to get this I.D. resolved, and also to find out if it is a Texas native agave.