From the Senate historian: “Occasionally one party maintains such an overwhelming majority that it has become necessary for majority party members to sit on the minority party side in the Senate Chamber. During the 60th Congress (1907-1909), 10 Republicans sat on the Democratic side, while during the 75th Congress (1937-1939), 13 Democrats sat on the Republican side. Such seating became known as the ‘Cherokee Strip,’ a reference to the region in Oklahoma, which was land belonging neither to the Indian Territory nor to the United States. By the 1930s, it had become the practice for senior senators to take front row, center aisle seats; junior majority party members who filled the “Cherokee Strip” were assigned either rear row or end seats on the minority party side.”
The last time a “Cherokee Strip” existed in the Senate Chamber was during the 76th Congress from 1939 to 1941. Six of the 69 Democratic senators sat with the 23 Republican and 4 Independent senators.