Longest Distance RUNNING completed!

I completed 8.7 miles this morning. I ran for 8 (only having to slow down to cross the roads) and then walked the remaining .7 miles. It was a fairly cool morning (compared to the humidity we have had the last 2 weeks)....so I headed out from the house at 5:30am. Got to my location and set up/stretched and began at 6am.
It was beautiful and for the first hour I only saw 3 people during my journey. Of course, on the return trip back to my vehicle, plenty of people were out and about.
One issue I've encountered (which happened the last time I did the long distance) is around mile 6 my upper leg muscle on my right side starts hurting, bad. I ended up having to stop twice to stretch (and also pop my lower back) to even complete my task. Of course, all day long I've been sitting here alternating ice and heat on my leg. I really need to figure out how to keep this from happening. It's gonna be an issue once 10K race time comes around, and it will REALLY be an issue come half marathon time next spring.