Methuselah is located between 2,900 and 3,000 m above sea level in the "Methuselah Grove" in the Ancient Bristlecone Pine Forest within the Inyo National Forest. Its exact location within the grove is a secret protected by the United States Forest Service.
Methuselah’s age was discovered in 1957 by Edmund Schulman, a dendochronologist from the University of Arizona. Schulman had spent the 20 years prior, traveling around the United States to find unusual, ancient, and undiscovered trees.
Schulman hit the jackpot when he visited the White Mountains and found that many of the trees were over 4,000 years old. One tree stood out and at the time was 4,789 years old. Schulman dubbed this tree Methuselah, after the oldest person in the Bible who lived to 969 years. Since Schulman’s discovery, the grove that Methuselah is located in has become famous and was named after the most ancient tree.
Fighting the elements for millennia, bristlecone pines have been exposed to extreme cold temperatures, dry soils, high winds, and short growing seasons. Being in a category known to many scientists as extremeophiles the trees grow very slowly.
Bristlecone wood is very dense and resinous, and thus resistant to invasion by insects, fungi and other potential pests. In very old specimens, often only a narrow strip of living tissue connects the roots to a handful of live branches.
According to oldest.org; en.wikipedia and usda.gov