chinaberry (melia azedarach)?

Maybe? I've never seen berries or flowers on it, though.

Aralia sp?

Doesn't seem to be so.

some type of elm?

Could there be two different plants in there? Can you trace the stems down Both appear to be pinnate leaved but the lower one has much smaller denser leaves.

Looks like a Golden Rain Tree to me. Very, very invasive. I suggest you cut it down and put stump killer on the stump. Definitely not an elm or aralia. It's in the wrong place for a 50' tall tree, and trust me, you don't want to spend the rest of your life killing off seedlings, like I'm doing because of several next door to me.

Goldenrain tree was my first reaction but I'm not sure. Wait on the destruction of the plant until you get a more definite ID.

FataMorgana

if its not Koelreuteria then its Gymnocladus, either way, its a tree and needs to be moved.

I agree with fatamorgana: I don't want to cut it down if that's not what it is.

I took a few more pics to see if it helps. Fata, you are right about it being more than one plant. There are three. Here is a pic of the three "trunks."

{{gwi:143386}}

Here is a picture of some new growth on the medium-sized one.

{{gwi:143387}}

Here is one "frond/branch" in almost its entirety.

{{gwi:143388}}

And this picture shows where the "fronds/branches" attach to the main stem or trunk.

{{gwi:143389}}

Koelreuteria for certain.

Ok, I'll cut it down tomorrow. Removing all these invasive plants is sure leaving holes in my landscaping!

Koelreuteria bipinnata isn't entirely bad. I'd move it to another location
and watch it closely. It's cousin koelreuteria paniculata is a real pest.

Here is a link that might be useful: koelreuteria-bipinnata

How would I know which one I have?

Yours is bipinnate, hence it's name.

Here is a link that might be useful: Compound leaf

You said to watch it closely? What am I watching for?

Tendency to spread out by seed to natural areas nearby.

Ok, thanks! :)