The National Threshers Association (NTA) is a non-profit group of enthusiasts who are interested in steam-powered traction engines - also known as "steam tractors", "steam traction engines" or simply "steam engines" - as well as related equipment. The group's premier event is its annual reunion/show, which features live exhibits of antique steam engines and gas-powered machinery from throughout the United States and Canada. Dating back to 1944, the annual show is recognized as the oldest event of its type in the United States.