jwood......The Colt Single Action Army or as it was called the "Peacemaker" is the most collectable revolver in the world. The 1st Generations are normally considered to have been manufactued from 1873-1940. It was made in over 35 different calibers and all kinds of various configurations. Values of these revolvers can fall all over the place according to condition, configuration, special features etc. If yours is of standard configuration and has a serial number number range between 54,000 to 130,000 it would have been built between 1880 and 1890. It can have a value as high as approaching $40,000 to as low as $4500 - $5000.....again according to originality and condition.
Caution should be noted here as the late Kieth Cochran, a true Colt expert, who was the author of the Colt Peacemaker Encyclopedia, stated that sadly that it is estimated that over 1/2 of all the Pre WWII revolvers are no longer original.
I can highly recommend that the first thing to do is to obtain a Factory Archive Letter on your revolver. Although not totally infallible, these letters are usually very accurate. You can obtain them by getting in touch with Colt Archive Properties LLC located at 1295 Blue Hills Avenue, Bloomfield Connetticut, 06002. The letters cost between $100 to $200, the last time I had one done. You can also call them but it cost more.
It is very much worth the money spent and will verify the originallity of your revolver and will greatly add some value to your gun.Once you have that letter and can verify all the serial numbers matching, etc....then you can get a very accurate value of your gun.
If all ends up being accurate and looks pretty promising, and your revolver is in fairly good condition I would definitely have it proffesionally appraised by a reputable collectable firearm appraisal like Rock Island or similar. I use a man in Missouri who has been collecting Colts for about 5 decades to help me with mine.
Dont take it to a buy and trade typical gun shop for appraisal. They will typically either over appraise it or under appraise it in efforts to buy it off you.
Invest in the factory letter, it will verify a lot for you and then go from there.
Initially it sounds like you have a wonderful piece of American history!