Back in the Silver Age, comics were a little simpler and more of a family thing.
That even held true for Gotham's guardian, the Batman, as he had young ward Robin, extra-dimensional Bat-Mite, butler Alfred Pennyworth, police Commissioner James Gordon, gal pal Batwoman, her niece and partner Bat-Girl...
...and, mostly importantly...Ace the Bat-Hound!
Dark Dog Days Begin
Ace started his career in
Batman #92 (June, 1955) in the story "Ace, the Bat-Hound" by writer
Bill Finger and artist
Sheldon Moldoff, wherein Batman and Robin help a lost dog, the dog follows Batman and Robin on a case, and due to its distinctive marking, Robin makes Ace a mask.
The dynamic duo then find out Ace's owner, John Wilker is missing, and the trio track him down, saving the man (and still protecting Bruce's identity).
This story ended up being reprinted in
Batman from the 30s to the 70s,
Batman Family #5 and in the
Batman in the Fifties Tradepaperback...
...though, sadly, most of Ace's appearances haven't been collected....
The Bat-Hound Returns
It starts with Ace's second appearance in
Batman #97 (February, 1956) wherein Batman borrows Ace from Wilker to track down a thief using dogs in his crimes, then to
Batman #103 (October, 1956) with the Bat-Hound becoming a movie star (Holy Rin-Tin-Tin, Batman!).
Batman began to see the use of the Bat-Hound.

Batman saving Ace from a villain who planted a bomb in his collar in
Detective Comics #254 (April, 1958 in Ace's only Detective Comics cover), Ace helping Robin to track down "The Fugitive Batman" in
Batman #123 (April, 1959, with a cover by
Curt Swan, who would later be known more for being Superman's artist), and finally becomes Bruce Wayne's pet when John Wilker goes travelling in
Batman #125 (August, 1959....Ace's first cover that he wasn't on....though the story is reprinted in
Batman Annual #7 of 1964, which was reprinted in the
Batman Annuals Volume 2 Hardcover).
Ace continued to appear on occasion, like
Batman #130 (March, 1960),
Batman #131 (April, 1960),
Detective Comics #280 (June, 1960), and then
Batman #133 (August, 1960), wherein Ace makes the cover again (and works with Batwoman and Bat-Mite...
...and this story makes it into
Batman Annual #7 and thus the
Batman Annuals Volume 2 Hardcover as well).
Ace just didn't have a chance in the early sixties, as Batman faced more alien menaces and strange criminals (who took up more of the coveted cover space on issues
Detective Comics #287 of January, 1961,
Batman #140 of June, 1961)....
...but at least he shared the space with the latest bug monster in "Bat-Hound and the Creature" in
Batman #143 (October, 1961) before disappearing again with
Detective Comics #306 (August, 1962),
Detective Comics #307 (September, 1962),
Batman #152 (December, 1962),
Batman #156 (June, 1963),
World's Finest Comics #134 and
#135 (June and August, 1963) and
Detective Comics #318 (August, 1963), and getting his last cover with
Batman #158 (September, 1963) showing off new, temporary super-powers!
Ace then showed up in
Batman #162 (March, 1964, reprinted as a part of
Batman: The Black Casebook Tradepaperback which came about because of writer
Grant Morrison's putting some of Batman's 1950s and early 1960s adventures back into Batman's history), and then Ace made his final Silver Age story in
World's Finest Comics #143 (August, 1964, where Ace met the Nighthound, a partner of Superman's Nightwing identity, Superman's version of Batman in Kandor, which oddly has been reprinted a few times, in
World's Finest Comics #197,
Superman: the Bottle City of Kandor and in
Showcase Presents: World's Finest Volume 2!).
Another version of Ace returned in starting with
Batman #462 (May, 1991 by
Alan Grant and
Norm Breyfogle) and there was even an animated partner of
Krypto the Super-Dog version of Ace for a time, as well as being the elder Bruce Wayne's loyal dog in the
Batman Beyond animated series and appearing in
Batman: Brave & the Bold animated series as well in a more classic version, and even helped Scooby-Doo recently in
Scooby-Doo Team-Up #2! Zoinks!
You just can't keep a good dog down!