Hey folks, thanks for the helpful responses. I cleaned all the ground wire connections and bought a new battery and it started right up.

I thought the battery was not the limiting factor because I had tried jumping the car AND had tried starting it off my brother's van battery (nearly identical specs), but I've learned I don't understand batteries very well.

Diseasal 300 - thanks for pointing out that I was testing the starter motor wrong. This made me hesitate (and not spend all day pulling my starter motor out of the vehicle), which is a big help. I was wondering if I was doing it wrong, which is why I posted the vehicle. So thanks for the response.

NZ Scott - you were totally right that I had a shortage of current problem. I'm still not sure why it wouldn't start with the borrowed battery I tried....

Anyway, thanks for the help. Started it a few times since then and it starts more easily than it ever used to. The battery has probably been weak for a long time.