I have never heard of "steenth" but here in Minnesota, many use the made-up word "umpteenth" in the same context.....anybody else heard of this?

Same here...I've heard of umpteenth, but "steenth" was new to me as well.

Ditto on 'umpteenth', never 'steenth'.
Also "to the Nth degree", similar.

Ditto for me on "umpteenth," which I've always heard pronounced without the "p": umteenth. It goes back at least to the Depression years according to my father, who uses it regularly. Never heard of "steenth."

There is also "Juneteenth," which is a quasi-holiday that originated (I think) in east Texas to commemorate the day that the local black population learned of (I think) the fall of the Confederacy at the end of the War Between the States. Somebody will have to look all this up, because I don't plan to, but (I think) it is June seventeenth.

Also, "steenth" is a very ugly-looking word. It looks like the name of a combined surgical-dental device, something one would expect to see in a metal pan somewhere in a garishly-lit clinic having aquamarine walls.

We also have "Juneteenth" celebrated here. Don't know when it
is, either, and really don't care, but it uses the "teenth".

Juneteenth

It is a portmanteau of June 19th, the day in 1865 on which slavery was abolished in the State of Texas (link).

Thanks for taking the time to look it up.
35 States and DC celebrate it. I know we do with a parade and
some orations and the like.

Steenth is (or was) a financial term meaning 'one-sixteenth of a point'. Dunno if it's still used since they've gone to metric in quoting stock prices,