You mean there is an East Wacker and a South Wacker?
Do the Wackers ever meet?
The Chicago River used to flow into Lake Michigan (the flow was reversed by the Army Corps of Engineers). About 3/4 mile inland the river divides into a north fork and a south fork. If you follow the river inland from Lake Michigan and then along the South Fork, the street to the immediate south and east of the river is Wacker Drive. Wacker Drive is called East Wacker Drive from the lake to State Street, then it is called West Wacker Drive until the corner where the river forks. It is called North Wacker as it goes south from the fork to Madison Street, and then it is called South Wacker Drive.
Simple enough?