Comic Title: Action Comics #258
Publisher: DC (National Comics Publications, Inc.)
Address: 575 Lexington Avenue, New York, NY
Cover Date: November 1959
On Sale Date: September 29, 1959 Newsstand Date September 29, 1959
Source: House Ad, Superman's Girl Friend Lois Lane #13, Page 20

Copyright Date September 29, 1959
Source: Library of Congress, Periodicals 1959

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

Title: "Supergirl's Farewell to Earth"
Pages: 8

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

Writer: Otto Binder
Artist: Jim Mooney

Reprinted In:
Action Comics #373 (1969)
Supergirl Archives Vol. 1 HC (2001)
Showcase Presents:Supergirl Vol. 1 TPB (2008)
Supergirl:The Silver Age Omnibus Vol. 1 HC (2016)
Supergirl:The Silver Age Vol. 1 TPB (2017)

Feature Character(s)

• Supergirl (last appearance in Action Comics #257; next appearance in Action Comics #259)

Guest Star(s)

• Superman (last appearance in Action Comics #258; next appearance in Adventure Comics #266)

Supporting Character(s)

• Mr. Dixon (last appearance in Action Comics #253; next appearance in Action Comics #262)

Guest Appearance(s)

• Krypto (last appearance in Superman #130; next appearance in Superman #134)

Other Character(s)

• Two small children (no further appearances)

Comments:
Supergirl learns Superman’s secret identity in this story.

Synopsis:
While saving two children from a falling tree, Supergirl spots Krypto. She introduces herself to the super-dog and plays with him. Superman arrives and is upset that Supergirl revealed her existance to his dog. He exiles her to an asteroid for a year.

From the asteroid, Supergirl keeps an eye on Earth and even puts out a forest fire. Krypto arrives a week later and warns Supergirl of a kryptonite cloud approaching. She is allowed to return to Earth for one day.

Her absence as Linda Lee has caused people to look for her. She gets her clothes dirty and pretends to have been lost in a swamp. Amazed by the girl’s ability to survive, a reporter checks her for mosquito bites. When he finds none, he guesses that she is a super-girl. Linda removes her disguise and reveals herself to the reporter. Then she tells the reporter that he is Superman. The reporter was Clark Kent.

The whole exile was a test by Superman to see if Supergirl could protect her secret. He wanted to see if she was worthy to learn his secret identity. She found out by herself which proved her ability to Superman.