John T. McKee's extraordinary head size was first documented in 1890, when he was measured at the World's Fair in Chicago. His head was so large that it was displayed as a curiosity, drawing significant attention from medical professionals and the public alike. The measurement was taken using a simple tape measure, and the result was recorded as 22.5 inches, a record that stood for over a century.
The cause of McKee's giantism remains a subject of debate among medical historians. Some speculate that it was due to a rare genetic condition, while others suggest that it may have been influenced by environmental factors, such as malnutrition or hormonal imbalances during his early development. Regardless of the exact cause, McKee's head size was a unique anomaly that captured the imagination of the time.