“Thar’s gold in them thar hills” (or “There’s gold in them thar hills”) is a clichéd saying, supposedly originating in American gold mining of the 19th century. There is no evidence that M. F. Stephenson and the Dahlonega, Georgia, gold rush inspired the phrase. Mark Twain’s character of Mulberry Sellers is often given credit for saying this in the novel The American Claimant (1892), but the saying does not appear there.
 
“There’s gold in them hills” has been cited in print since at least 1906; “There’s gold in them thar hills” was called an old-time line in 1922. The line is still used, especially in the gold industry.
 
A jocular riddle on the saying is:
 
Q: Why did the non-binary prospector move to California?
A: There was gold in them/their hills.
   
     
Wikipedia: Dahlonega, Georgia
Dahlonega is a city in Lumpkin County, Georgia, United States, and is its county seat. As of the 2000 census, it had a total population of 3,638.
 
Dahlonega is located at the north end of Georgia 400, which connects Atlanta to many affluent suburbs to the north. It is consistently named as a best place to retire by many different publications due to its low cost of living, vibrant activities, continuing education for seniors, festivals, and beautiful setting.
 
In 1828 Dahlonega was the site of the first major gold rush in the United States. The Dahlonega Gold Museum Historic Site sits in the middle of the town square, housed in the old Lumpkin County Courthouse built in 1836. From its steps in 1849, Dahlonega Mint assayor Dr. M. F. Stephenson tried to persuade miners to stay in Dahlonega instead of joining the California Gold Rush, saying, “There’s gold in them thar hills.”
 
Wikipedia: M. F. Stephenson
M. F. Stephenson (born 1801), whose full name was Dr. Matthew Fleming Stephenson, was born in Virginia. On February 25, 1836, he married Sarah Elizabeth Sumter Lyon. He was considered a Georgia geology and mineral expert, although there is no record of him receiving any formal education in the field of geology. He was one of the first collectors of lazulite, rutile, pyrophyllite, and other minerals.
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He served as the assayer of the Dahlonega Mint in Dahlonega, Georgia in the 1840s. When the gold rush in Georgia was believed to be over, many miners headed west to join the 1849 California Gold Rush. Stephenson thought differently and in the town square proclaimed to over 200 men, “Why go to California? In that ridge lies more gold than man ever dreamt of. There’s millions in it.” This excerpt was retold to Mark Twain by the miners who moved to California from Georgia and may have inspired his character Mulberry Sellers. Sellers was famous for his lines “There’s gold in them thar hills” and “there’s millions in it.”
 
30 August 1897, Omaha (NE) World-Herald, “Incident of the Fight,” pg. 2:
“I wonder if there is gold in them thar mountains. By—, I’ve got to find out, for I can’t get back without some.”
       
Google Books
The Story of “Scotty” (Walter Scott), Kng of the Desert Mne
By Charles A. Taylor
New York, NY: J.S. Ogilvie Pub. Co
1906
Pg 23:
“There’s gold in them hills, Slim, ” he muttered.
 
OCLC WorldCat record
There’s gold in that hill.
Author: James Denney
Publisher: Omaha, Neb. : Omaha World-Herald, 1911.
Series: Sunday World-Herald Magazine of the Midlands, January 17, 1971. 
Edition/Format:  Book : English
 
25 February 1912, Washington (DC) Post, magazine, “Gassaway Ben and the Devilfish,” pg. 5, col. 5:
“Boys, sea’e, whar thars smoke, thars shorely gotter be fa’r, and if I haint mistook great ways, thars gold in them thar rocks.”
   
28 February 1916, Mills County (IA) Tribune, “Old Jim’s Discovery” by H. M. Egbert, pg. 4, col. 2:
“I tell you,” he went on enthusiastically, “there’s gold in them hills.”
 
17 July 1920, Fort Worth (TX) Star-Telegram, “Buzzin’ Around with Billy Bee,” pg. 6:
The original Forty-niners went across the plains thrilled with the thought, “thar’s gold in them thar mountains, Clem,” but the nouveau Forty0eighters seem to think there’s dough in these here politics.
 
5 September 1922, Syracuse (NY) Herald, “Outlines of a Day’s History” by All’s Well, pg. 1, col. 2:
TWO old-time lines come out of memory cells and declare themselves immortal. One is “Back to the mines!” and the other, “There’s gold in them thar hills,” the gold meaning coal as the man who pays soon shall learn.
   
Google Books
Merton of the Movies
By Harry Leon Wilson
Garden City, NY: Doubleday, Page & Co.
1922
Pg. 167:
“Say ‘Thar’s gold in them hills!’ if you can’t think of anything else.”
 
Google News Archive
15 May 1925, Pittsburgh (PA) Press, “Today” by Arthur Brisbane, pg. 15, col. 5:
“There’s gold in them mountains,” the old prospector used to say. There is, if you know where to find it. But, there’s a good deal more gold in oil wells, if you know how to locate them. And, apparently Mr. Doheny does know.
 
7 February 1926, Charleston (WV) Daily Mail, Magazine, “The Potters” by J. P. McEvoy, pg. 3, col. 1:
BILL: (with an oracular gesture to include the flat Florida landscape) Woman, there’s gold in them that hills.
 
Google Books
Banking: journal of the American Bankers Association
Volume 22
1929
Pg. 818:
As the saying goes — “thar’s gold in them thar hills” — so there’s money and a future in the business of a country bank.
 
Google News Archive
2 May 1929, St. Petersburg (FL) Evening Independent, “In New York” by Gilbert Swan, pg. 2, col. 1:
When the talking pictures brought the theme song into the national limelight, the voices of the bankers and the movie magnates could be heard whispering…“there’s gold in them thar trills, stranger!”
 
Google Books
Trail and Timberline
Issues 135-170
Colorado Mountain Club
1930
Pg. 31:
Within a few weeks after the classic ‘There’s gold in them thar hills” had been whispered, a hundred or more buildings would be up — saloons, stores, dwellings.
 
OCLC WorldCat record
There’s gold in them hills : the saga of a colonial cove.
Author: Donald Lindsay Gordon Mundy
Publisher: Christchurch : Printed by Simpson & Williams, [1948]
Edition/Format:  Book : English
 
OCLC WorldCat record
There’s gold in them hills near Great Falls, Maryland : the story of gold mining since the Civil War
Author: Robert Shosteck
Publisher: Silver Spring, Md. : The Author, 1953.
Edition/Format:  Book : English
 
OCLC WorldCat record
There’s gold in them thar cans.
Author: IH HUNT
Edition/Format:  Article : English
Publication: Canadian hospital, 1960 Oct; 37: 48 passim
Database: From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.