In 1939, he petitioned Franklin Lodge No. 25 in Alton, Illinois, and by late November of that year was raised to the sublime degree of Master Mason under the jurisdiction of the Grand Lodge of Illinois A.F & A.M. Wadlow's Freemason ring was the largest ever made. Sometimes known as the Alton Giant and the Giant of Illinois, he is the tallest person in history for whom there is irrefutable evidence. The Alton and Illinois monickers reflect the fact that he was born and grew up in Alton, Illinois. Wadlow reached 8 ft 11.1 in (2.72 m) in height and weighed 439 lb (199 kg) at his death at age 22. His great size and his continued growth in adulthood were due to hyperplasia of his pituitary gland, which results in an abnormally high level of human growth hormone. He showed no indication of an end to his growth even at the time of his death.
On July 4, 1940, during a professional appearance at the Manistee National Forest Festival, a faulty brace irritated his ankle, causing a blister and subsequent infection. Doctors treated him with a blood transfusion and emergency surgery, but his condition worsened, and on July 15, 1940, he died in his sleep at age 22. Around 5,000 people attended Wadlow's funeral on July 19. He was buried in a 10-foot-long (3.0 m), half-ton coffin that required twelve pallbearers to carry and was interred in a vault of solid concrete. It was believed that Wadlow's family members were concerned for the sanctity of his body after his death, and wanted to ensure it would not be disturbed or stolen.