On September 21st, 2015, I completed a running circumnavigation of Mono Lake, the iconic body of water just east of Yosemite NP. The entire route is 41.7 miles long. I have found no reports of anyone else doing a loop run around Mono Lake, so as of now I believe this to be the first time it has been done. My time was a modest 9h03m. I ran unsupported, carrying all necessary water and food, plus dipping into a natural water source near the end. I still don't own a fancy watch so if you're concerned about verification, check the timestamps.
Google Earth flyover video of the route here: www.youtube.com/watch?v=14JQAlmsjH4