Comic Title: Adventure Comics #251
Publisher: DC (National Comics Publications, Inc.)
Address: 480 Lexington Avenue, New York, NY
Cover Date: August 1958
On Sale Date: July 1, 1958 Copyright Date July 1, 1958
Source: Library of Congress, Periodicals 1958

Frequency: Monthly
Cover Price: $0.10
Page Count: 32
Editor: Mort Weisinger

Title: "Superboy's Last Day"
Pages: 12

Feature(s):
Superboy (of Earth-1)

Writer: Otto Binder
Artist: George Papp

Reprinted In:
Superboy #165 (1970)

Feature Character(s)

• Superboy (last appearance in Adventure Comics #250; next appearance in Superboy #67)

Supporting Character(s)

• Jonathan Kent (last appearance in Adventure Comics #250; next appearance in Superboy #67)
• Martha Kent (last appearance in Adventure Comics #250; next appearance in Superboy #67)
• Lana Lang (in flashback; last appearance in Adventure Comics #170; next appearance in Superman #136)

Other Character(s)

• Superboy’s robot Friday (no further appearances)
• Dr. Lewis (in flashback; no further appearances)

Flashback Appearance(s)

• Superboy (last appearance in Adventure Comics #170; next appearance in Superman #136)
• Jonathan Kent (last appearance in Superboy #17; next appearance in Adventure Comics #172)
• Martha Kent (last appearance in Superboy #17; next appearance in Superboy #18)

Comments:
Superboy’s first encounter with Kryptonite is related in flashback in this story.

Synopsis:
Whle cleaning house, Clark Kent recalls how one of his Superboy robots saved his life. Many years before, Pa Kent brought home a green glowing rock for Clark’s mineral collection. Clark immediately took ill and was on his deathbed. To replace him as Superboy, a recently constructed Superboy robot was sent out controlled by Jonathan.

When the robot returned, it inadvertently stepped in front of the Kryptonite. Being made of lead, the robot blocked the radiation. Superboy recovered but relapsed when the robot moved away. Pa Kent realizes that the rock must be responsible and places it inside the robot. Superboy recovers and learns that the rock was Kryptonite, a fragment of his home planet, which is deadly to him.