We had offshore races for two years here in Milwaukee.
I have emailed both the APBA and OSS and neither of them have Milwaukee on their schedule again this year.

Does anyone who it was that held those races and what happened to this venue?

in 2003 was APBA

Following the Key West worlds in 2004 SBI, in FL (SuperBoats) was awarded the rights to promote and run the APBA offshore races. They are running combined races under SBI, so you might try to contact them.

Milwaukee costs too much for promoters. The city sticks it too hard to make any profit.

Sure is a shame. Racers loved the course here. Maybe some day they will try again.