During 1948, the United States Corps of Engineers started construction of the flood control dam and created East Branch Lake.

The dam inundated the two settlements in the valley. The town of Instanter was a depot on the Johnsonburg & Clermont Railroad and also was the site of the Schultz and Hoyt Tannery. The second village was Straights, from which the nearby Civilian Conservation Corps (CCC) Camp 83 got its name.

Remnants of both Instanter and Straights can be seen during low pool levels.

Development of Elk State Park was completed in 1963, and during 1970, DCNR’s Bureau of Forestry turned 2,022 acres over to the Bureau of State Parks and increased the park’s size to a total of 3,192 acres.