This is not a satisfactory image of this dead and dried out spider but it was so large I wanted to find out what it was. Several thought it was a tarantula which it is not. There were two (including an entymologist) who thought it was a wolf spider (lycosidae) and it well may be. Another person thought it was a fishing spider (pisauridae) -
Apparently fishing spiders have two rows of eyes while wolf spiders have three rows of eyes. If fishing spiders live in Missouri then that is possibly what this is but it is difficult to tell because of the poor quality of the image close-up. Perhaps the aquatic insects and small fish in Lake Aspen are resting more easily.