Ma and Pa Kent
When the first Superman story appeared in Action #1 and again in the first newspaper strips, there was no mention of who found Kal-El's rocket. Or where and how Clark grew up.  Just a statement that a passing motorist turned the baby into an orphanage.  Presumably he grew up there.  However in Superman #1, an elderly couple, the Kents are introduced into the story line.  Mary is named on page 1.

When the radio show premiered, the producers changed the origin so that Clark lands on Earth as an adult.  But when George Lowther's novel appeared in 1942, he named Clark's foster parents Eben and Sarah, names that were later used in the TV show.

The next origin sequence to appear was in 1944, the first appearance of Superboy.  The Kents are once again unnamed.
A December 1945 Sunday newspaper sequence also did not name the Kents.

In the October 1947 radio serial, "The Secret Rocket", Clark's father is once again called Eben Kent.
(and his rocket lands in Centerville, Iowa).

In August 1948, Superman 1953, Clark's parents are called John and Mary Kent, but in the 1948 movie serial Clark's parents are called Eben and Martha Kent!.
In May 1949, Pa Kent was called Silas in Action 132.

"The Secret of the Kents" by Bill Finger, Wayne Boring and Stan Kaye.

He finally became Jonathan Kent in Adventure 149, February 1950, after the Superboy strip had been running for 6 years! 

The Smallville General Store first appeared in Superboy 6, in January 1950.

"The Fake Superboy" by Ed Hamilton, John Sikela and Ed Dobrotka.


Ma Kent was called Marthe in Superboy 12 January 1951.

"Superboy's Problem Parents" by William Woolfolk, John Sikela and Ed Dobrotka

By Action 158, July 1951 her name had been modified to Martha.
The last major change in the Kents, up until the late 60's was the decision to give Dad Kent hair in Adventure 198 in March 1954.

"The Super Carnival from Space".  Art by Curt Swan and John Fischetti.

In March 1968, the Kents were rejuvenated by a mysterious force in Superboy 145.