He was also a member of the Isthmian Canal Commission and civil governor of the Canal Zone from 1910 to 1913. Thatcher was the Commission's longest-lived and last surviving member.
During his congressional tenure, he guided the passage of several Kentucky landmarks and parks: Mammoth Cave National Park, Lincoln's birthplace, and the Zachary Taylor National Cemetery. He gave up the Republican nomination in 1932 to retain his House seat in order to run for the Senate, which he lost.
Thatcher was served on the general counsel of the Gorgas Memorial Institute of Tropical and Preventative Medicine, Inc., Washington, D.C beginning in 1939 and became vice president in 1948, a post which he held until 1969 when he was made honorary president, a position only previously reserved for Presidents of the United States.
He was the longest-lived person ever to serve in the United States Congress.