They are located at the easternmost end of the Yosemite Valley floor.

[1] Happy Isles is also the trailhead for popular hiking destinations along the Mist Trail (including Vernal Falls and Nevada Falls) and Half Dome.

Happy Isles is located where the slope of the Merced River changes from the much steeper upper main stem to the essentially flat Valley floor.

The gradient of the Merced River at Happy Isles is steeper than in the Valley floor, and the channel of the river is cut into erosion-resistant granitic boulders and talus materials, compared to channel deposits of sands and gravel present on the Valley floor.

The steeper gradient and composition of streambed materials together impede meandering patterns from developing in this area.