Anything previous to the first world war would be considered antique. In my state anything that shoots black powder and loads from the muzzle is not even considered a firearm. I don't recommend people new to black powder shoot antiques, there are replicas made that are identical to the originals and fabricated of better steel. I have a few such, mostly pistols and they are a literal blast.
Now while here in Masterbachusetts you can buy a bp handgun without any greater hassel than putting the money down, but you need the FID to get powder. I would also not recommend planning to use a black powder handgun for home defense, due to the hygroscopic nature of black powder. It isn't a good idea to leave a loaded primed bp handgun in the desk drawer or night stand (unless you have a dehumidifyer in there with it, to keep the powder from attracting moisture and corroding the bore). You could simply fire it and clean and reload it frequently, that is what the old timers did, but you can't put it in a box loaded and leave it without consequences, aside from it just being poor gun safety to do so.

1900 Is probably the date, I did generalize a bit, I know a lot of pre 1900 guns are perfectly safe to fire, except for the ones that aren't that is...My local gun shop has a Broomhandle Mauser I been oogling for some time. If it were a Red 9 I would have gone into hock to get it, but it is the 7.65mm bottlenecked cartrige and it would be a dear thing to feed. Of course a Broomhandle Mauser uses smokeless powder not black, but it is still an antique.
BTW Del,it was 9 farenheit outside this morning and about 45 in the kitchen (damn pipes froze up agin) so gimme a month or so on the bathing suit picture, Its just too cold yet. I don't want to post just any picture on the web-my liberal friends think of me as the gun nut so I feel I have to achieve a certain standard what with the booth babes and all...

1910's-1920's?

yep, my grandpa had one colt and he would take it on hunting trips just to tag along,

ATF Publication 5300.11, Firearms Curios and Relics List, consists of lists of those firearms determined to be curios or
relics from 1972 to the present.

http://www.atf.gov/publications/firearms/curios-relics/

To be recognized as C&R items, 478.11 specifies that firearms must fall within one of the following categories:

Firearms which were manufactured at least 50 years prior to the current date, but not including replicas of such firearms;
Firearms which are certified by the curator of a municipal, State, or Federal museum which exhibits firearms to be curios or relics of museum interest; and

Any other firearms which derive a substantial part of their monetary value from the fact that they are novel, rare, bizarre, or because of their association with some historical figure, period, or event.

Firearms automatically attain C&R status when they are 50 years old. Any firearm that is at least 50 years old, and in its original configuration, would qualify as a C&R firearm. It is not necessary for such firearms to be listed in ATF’s C&R list. Therefore, ATF does not generally list firearms in the C&R publication by virtue of their age.