The first costumed Manhunter from DC originally appeared in Adventure Comics #73 (April 1942).
But prior to that, DC had a feature called "Paul Kirk, Manhunter" that began in Adventure Comics #58 (January 1941).

That feature ran through issue #72 (March 1942).

The following issue (Adventure Comics #73, cover-dated April 1942) saw the introduction of a costumed character named "Manhunter":

but for some reason, he was referred to as "Rick Nelson" for this episode.
When the feature returned for issue #74, the character was now named "Paul Kirk", but there did not seem to be any connection to the previous "Paul Kirk, Manhunter" feature that had previously ran in that title.
Also, when DC later reprinted the Manhunter story from Adventure Comics #73 years later in The New Gods #4 (August-September 1971) they changed the name from "Rick Nelson" to "Paul Kirk".


In Detective Comics #437 (October-November 1973), Archie Goodwin and Walter Simonson would begin their series featuring Paul Kirk revived in the "present day" (of 1973).