Following rumors of large gold fields to be found in southern Idaho, George Grimes and Moses Splawn were leading a small group of prospectors when they discovered gold in the Boise Basin on August 2, 1862.
It all started with a story told to Splawn a year earlier by an Indian who said that there was so much gold laying about that it could be picked up by the handfuls. The prospectors initially found some placer deposits in the Boise River, which they traced upriver to the creeks that flowed through the Boise Basin. These creeks would eventually be named Mores Creek and Grimes Creek.
Here, they found the gold they were looking for. Unfortunately for Grimes, he was killed within just a few days of the find. Some say he was killed by a greedy partner, but the accepted story is that he was killed by Indians. His partners buried him in a prospect hole in a mountain pass, which is now called Grimes Pass.
The discovery party then returned to Walla Walla, Washington with $5,000 in gold and the news of the strike. In the fall they headed back to the Boise Basin with about 50 men. At this time, the area was a wilderness area inhabited only by the Indians. However, as word of the gold discovery traveled, this would quickly change and the gold rush was on. Many people traveled by steamer up the Columbia River to Umatilla, Oregon departing from Umatilla by stage lines, and finally journeying by pack-train to the Boise Basin.
The Boise Basin gold rush was the largest since the California gold rush a dozen years earlier. For a hard-working gold miner in a good location, a week of prospecting could yield $2000 per week. Within eight months of the strike, the area would become the largest settled area of the Pacific Northwest.
As the growing number miners began staking claims, a number of boom towns erupted including Placerville, Centerville, Pioneerville, and Idaho City.
Situated along Grimes Creek, the first camp at what would become Idaho City was established by Captain Jeff Standifer. A town was officially founded on October 7, 1862, by J. Marion More, a member, of the Splawn-Grimes discovery party. The town was first called Bannock City. In March 1863 it took on the name of West Bannock, and in December 1863 it was changed to Idaho City by the new Idaho Territorial Legislature to avoid confusion with Bannack, Montana.
J. Marian More, the founder of the town, became very wealthy from his prospecting and eventually would own several mines around Idaho City. Later, he began buying mines in the Silver City area, where he was involved in the Owyhee Mine War which resulted in several killings. More, himself, would be shot down in Silver City in 1868.
Although Placerville enjoyed the advantage of a location convenient to the point at which the gold rush entered the Basin, Idaho City boasted greater growth and prosperity because it had a better water supply. It quickly grew into more than just a mining camp. Readily available timber made it possible to build permanent structures quickly, turning the tent town into a flourishing city.
At the time of the gold rush, Idaho was still a part of Washington Territory and the Boise Basin was located in Idaho County, of which, Florence was the county seat. Because Florence was remote from the new mining basin, the Washington Legislature established Boise County on January 29, 1863. The Governor of Washington assigned William Noble, Frank More, and John C. Smith as commissioners and instructed them to establish the County seat at Idaho City. The first county officers besides the commissioners were Sheriff, Sumner Pinkham; Probate Judge Daniel McLaughlin; Auditor, W. R. Underwood; Treasurer, Charles Vajin; and Assessor George Goodman.
When Congress created Idaho Territory on March 4, 1863, Boise County exceeded the other counties in both area and in population. Those in office in Boise County retained their positions until the territorial government could be officially organized.
Before the community was a year old, Idaho City had 250 places of business including three express offices, three livery stables, a mattress factory, four sawmills, seven blacksmith shops, eight bakeries, nine restaurants, two bowling alleys, three pool halls, three drugstores, four breweries, and 20-25 saloons. Professionals included 15 doctors, 25 attorneys, and a photographer. The town also boasted two schools, a library, a newspaper called the Boise News, several churches, a hospital, and five community theaters. Building lots ranged in price from $500 to $2000 each.
Near the end of 1863, it was estimated that some 25,000 people were living throughout the hills, with 6200 of them living in Idaho City.