Grand Teton National Park is named for Grand Teton, the tallest mountain in the Teton Range. The naming of the mountains is attributed to early 19th-century French-speaking trappers—les trois tétons (the three teats) was later anglicized and shortened to Tetons. At , Grand Teton abruptly rises more than above Jackson Hole, almost higher than Mount Owen, the second-highest summit in the range. The park has numerous lakes, including Jackson Lake as well as streams of varying length and the upper main stem of the Snake River. Though in a state of recession, a dozen small glaciers persist at the higher elevations near the highest peaks in the range. Some of the rocks in the park are the oldest found in any American national park and have been dated at nearly 2.7 billion years.