April 23, 2023
Scan from an old comic book of the header image for the Ask the Answer Man column

Scan from the letters section from an old comic book. Q: Does Commissioner Gordon know that his daughter is Batgirl? Sandra Garrett. A: Yes.
Steel #1 (1977), via 13th Dimension

Maybe things were different in 1977, but in most Batman stuff I’ve read or seen it’s implied but never outright stated that the commish knows a secret identity or two, so I laughed at how blunt this answer is.