The first white men through the Wind River Canyon were the Ashley Fur Party in 1825. The original dam was built by Asmus Boysen in 1908, for whom the park and reservoir are named. Part of the original dam can still be seen adjacent to the tunnels on the Lower Wind River Campground. Mr. Boysen also built a 710kW power plant at the site. Operations ceased when in 1923 a major flood filled the plant with silt.
The CB&O Railroad went through the canyon in 1911 and the state highway went through in 1925. The existing dam was completed in 1951. Boysen became a state park in 1956.
Map: https://wyoparks.wyo.gov/index.php?preview=1&option=com_dropfiles&format=&task=frontfile.download&catid=404&id=38&Itemid=1000000000000