January 2, 1860
First county election held under provisional Jefferson Territory: Golden City selected as county seat; sheriff, clerk and recorder, and county judge elected.
January 9, 1860
First school in Jefferson County opens - the Golden City school - in a rented cabin at present-day 1304 Washington Avenue
January 14, 1860
Golden Gate City plat recorded.
January 16, 1860
Golden City Masonic lodge, one of the first Masonic organizations in Colorado, established.
April 6, 1860
First post office established at Golden City with Dr. Isaac E Hardy as postmaster.
August 26, 1860
All time hottest temperature in Jefferson County of 104 degrees recorded in Golden City.
September 1, 1860
The People's Court organized to address criminal matters in the district.
October 6, 1860
Birth of Charles L. Palmer, reputedly the first child of gold rush settlers to be born in Jefferson County. He serves as County Commissioner 1902 to 1909.
October 15, 1860
First major forest fire in Jefferson County. Burns for two months, charring Bear Creek, Turkey Creek and Mount Vernon canyons, and the whole of Green Mountain.
November 22, 1860
Golden City becomes capital of Jefferson Territory.
Three mining districts form and operate in central Jefferson County to administer extra legal law. Bergen (Bergen Park), Junction (Conifer), and Mt. Vernon (Mt. Vernon Canyon) Districts, then combined under the leadership of Thomas Bergen to form short-lived Ni-Wot County.
February 28, 1861
Congress combines pieces of Nebraska, Kansas, Utah, and New Mexico to create the Territory of Colorado. William Gilpin appointed governor.
November 1, 1861
Jefferson County is reorganized to become one of the original 17 counties created by Colorado Territorial Legislature.
November 16, 1861
Original Jefferson County Commissioners, John M. Ferrell, Spafford C. Field and George H. Richardson (appointed by Gov. William Gilpin), meet to organize upcoming county election. Original five districts of Jefferson County created.
November 19, 1861
Major windstorm damages 25 buildings in Golden City.
December 7, 1861
Election of county officers, including the first elected Board of County Commissioners.
January 6, 1862
Newly elected County officials assume office.
Jefferson County Commissioners reorganize county internally from five districts to the current three.
June 20, 1862
First county and school taxes levied by Jefferson County Commissioners.
June 21, 1862
First jail in Jefferson County built by Walter Pollard.
August 14, 1862
Golden City becomes capitol of the Territory of Colorado, remains so until 1867.
Henry Stevens, the first recorded homesteader in Jefferson County under the 1863 Homestead Act, builds his cabin at the current site of 44th and Teller streets in Wheat Ridge.
June 1, 1863
Locust plague hits the area, devastating everything in its wake.
May 14, 1864
First devastating flood in Jefferson County. It starts in Deer, Bear, Coal, and Mount Vernon Creeks, drowning thousands of sheep and 19 people in the South Platte. Flood wipes out all bridges on Clear Creek, compelling citizens to use ferries.
Colorado's first railway company, the Colorado Central Railroad Company, incorporated by William A. H. Loveland in Golden City.
February 9, 1865
Colorado and Clear Creek Railroad Company established.
August 5, 1865
First Baptist Church chapel, first church building in Golden, dedicated at the SW corner of present-day 12th and Jackson Streets.
- Jefferson County has a population of 1,782; Gilpin County has four times that
- The Loveland Building, one of the first brick buildings in Golden, is completed
- Clay mining begins in Golden with brick making at the Golden Brickworks
George West prints the first edition of his newspaper, the Colorado Transcript (now Golden Transcript) in Golden City.
- Territorial capital moves from Golden City to Denver City
- Astor House in Golden is built
- Last documented encampment of Arapaho tribe, led by Chief Friday, in Jefferson County
- Golden Paper Mills, only paper mill west of Missouri, established at Golden City, making paper from recycled rags and straw
January 1, 1868
Golden City celebrates the ground breaking for the first railroad construction in Colorado, by the Colorado Central Railroad Company.
April 8, 1868
Transcript forced to print its newspaper on yellow wrapping paper due to a severe paper shortage.
July 23, 1868
General Ulysses S Grant visits Golden City with fellow generals Sherman and Sheridan.
May 19, 1869
Eliza West (George West's wife) debuted her weekly column "Home Department" in the Transcript under the pen name Kate Warrenton.