The face value of the 1,427 coins, which date from 1847 to 1894, is around $27,000 (£16,000) but some of them are so rare they could sell for nearly $1m (£600,000) each.
The husband and wife made the find inside eight rusted metal cans as they walked their dog on their property in Gold Country, California, and now plan to sell most of the coins online.
David Hall, co-founder of Professional Coin Grading Service, which authenticated the find, said: "I don't like to say once-in-a-lifetime for anything, but you don't get an opportunity to handle this kind of material, a treasure like this, ever.
The coins were placed inside metal cans and buried
"It's like they found the pot of gold at the end of the rainbow."
The couple have chosen to remain anonymous, but have loaned some of the coins to the American Numismatic Association for its National Money Show in Atlanta on Thursday.
David McCarthy, chief numismatist for Kagin Inc in Tiburon, said: "Their concern was this would change the way everyone else would look at them, and they're pretty happy with the lifestyle they have today.
Some of the coins are so rare they could be worth $1m each
"It wasn't really until the 1880s that you start seeing coins struck in California that were kept in real high grades of preservation."
The coins came in $5, $10 and $20 denominations and would likely have been buried as soon as they were put into circulation. Most were minted in San Francisco.
The coin find, in April last year, is one of the largest in US history.
The couple stumbled over the hoard after seeing a tin can above ground
In 1985, construction workers in Jackson, Tennessee, found gold coins worth $1m (£600,000).
More than 400,000 silver dollars were discovered in the home of a man in Reno, Nevada, who died in 1974. They were later sold for $7.3m (£4.3m).
Gold coins and ingots thought to be worth as much as $130m (£78m) were recovered in the 1980s from the wreck of the SS Central America off the North Carolina coast.

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