According to this article in today's Guardian, the seven-inch single turns sixty-years old this month. What was the first commercially released seven-inch?

Eddy Arnold's "Texarkana Baby," originally released on 78rpm, then re-issued as a seven-inch by RCA on March 31st, 1949. To give you an idea how long ago that was, consider this startling fact: the flip-side did not feature a Sonic Youth side project.