"The mystery of life isn't a problem to solve, but a reality to experience"
Further info: In general there are VP markers for all the non-key VP you can get (exception: VPs to Habsburg and Protestant powers for control of Electorates post-Schmalkaldic League). For instance, there are several Master of Italy 1 VP markers, since you can get multiple VPs from the event being played more than once. Since there is only one VP marker for the Mississippi, it stands to reason you can only get that one VP.
True there are no markers, however I found that the electorate board pretty much can house the control markers necessary. You just have to remember to house-keep it once SL appears!