And there has been a clear upward trend in the average age of members over that time. There are exceptions—Democrat Maxwell Frost is the youngest at 27—but the average age of Americans over the last couple of years is 39.4, according to our research. The Senate average has gone from 59.8 years to 63.9 years. The oldest member during the 26 years of this century was Sen. Strom Thurmond at 99 in the 107th Congress. Republican Sen. Strom Thurmond of South Carolina was the oldest Congress member.