I am in SE WI and love Stanley! However, the one I grew lasted about 6 years and then got black knot so bad I cut it down. Too bad as the last crop it bore was 2 bushels of very tasty plums.

I am hesitant to replant a plum after that. Although I read that some varieties are less prone to black knot and Stanley is noted for being highly susceptible to it. Tests with Italian Prune plum where I work (at a nursery) were no better as all got black knot in one season.

Whatever you choose, make sure you have pollination covered as some plums are self-pollinating and some are not.

:( that is exactly what I'm hoping to avoid.

Thank you so much for your comment

The big issue is going to be finding something climate appropriate, AU Rubrum is a 650 chill hour plum developed by Auburn University for planting in southern and central Alabama. If you are not familiar with chill hours, you should read up on the subject as they control when a fruit tree will bloom in the spring.

According to the research that I've done thus far... The rubrum requires 700 hours and it is rated for zone 5.

Sources vary on 650 vs 700 chill hours, I planted one here in western Louisana last year, we have highly variable chill hours here ranging from 500 - 1,300. I don't know about your location or if you are in the urban heat bubble of Chicago. Picking a random suburb (Rockford, IL) for a chill hour calculator for last winter https://webapps.msucares.com/chill_hours/ I get about 1550 Chill Hours 32-45F using data from 2 random local weather monitoring stations.

Black Ice would be an option. It is hardy to zone 3, so it will take your cold just fine. It is reported to have above average disease resistance, but is moderately susceptible to Black Knot and Brown rot. If you spend a little time with sanitation in the fall, you should be ok here.