The Rocky Mountain Directory & Colorado Gazette for 1871 Comprising of a brief history of Colorado . . . pages 39 - 40. […these History pages were transcribed/posted by L. Ziemann, Arapahoe County Coordinator] 

ARAPAHOE. The first political division of that portion of the State of Kansas — now in Colorado — which embraced the Pike’s Peak gold region, was organized by the emigrants in and about Auraria, in the fall of 1858m and included all the region inhabited or explored at that time. Auraria was its principal town and county seat, and was the arena in which the political gladiators of those early days displayed their great prowess and endurance. The area then embraced by Arapahoe was much larger than that defined by the present boundaries, which were established by Government surveys, completed in 1861. 

These include a strip about 175 miles in length, east and west, and thirty miles in width, north and south; commencing at the eastern boundaries of Jefferson and Boulder counties, and extending to the Kansas line, east; and at the northern boundary of Douglas county, and extending the southern limits of Weld county, north and south. This belt lies entirely in the plains, or valley division of Colorado, and presents all the features peculiar to this district. It is watered by the Platte and many of its branches—principal among them, the Clear, Cherry, Kiowa, Bijou and Beaver creeks—also, by the Republican Fork of the Kansas. 

Although gold was first discovered, in paying quantities, within the present [1871] limits of Arapahoe county, the amount was trifling, and mining has never been a leading industry. No mineral deposits of commercial value, except coal measures, have been discovered; and these have not been sufficiently developed to establish their value or importance, though, no doubt, extensive lignite beds underlie the who extent of the county. 

Fossils and minerals, interesting to the student of geology, exist, however, in considerable quantities along the beds of water-courses and on the ridges, which receive notice in the appropriate chapter. With the exception of scattering cotton-wood forests, along the Platte and its tributaries, there is no timber in the county; but the usual vegetation of the plains is abundant everywhere, and the soil is very fertile and productive. This makes agriculture the leading industry of Arapahoe, outside of her principal cities, and has already grown to be of vast importance, and is attracting the attention of emigrants from all countries. 

Although the great portion of the soil of Arapahoe county, as well as that of other parts of the plains, requires irrigation, means of affording this are ample, and many thousands of acres of wheat, corn, and vegetables are already cultivated, annually, yielding large and profitable returns. Statistics illustrating this will appear in the chapter on agriculture, and should be carefully examined by those seeking profitable agricultural investments. 

Denver, the principal city and capital of Colorado—the Queen City of the Plains—is the county seat of Arapahoe county, and is located on the Platte river and Cherry creek, at their confluence, in the western central portion of the county. This is the mercantile and manufacturing centre of Colorado, as well as the most important city west of the Missouri river and east of the mountains, and has already a population of over 8,000 inhabitants, noted for their prosperity, thrift, and enterprise. They have already projected manufacturing enterprises which will, eventually, contribute largely to the general wealth of the country, and established commercial relations with the larger cities, east and west, of unusual importance, considering the age and location of the city. These, with all the resources, advantages, public buildings, institutions of learning, religion, etc., will receive full and detailed descriptions in our history of Denver, in which will also appear all statistical matter and gazetteer information concerning Arapahoe county. The history of Arapahoe county and of Denver are so intimately connected, we give them in detail in the same chapter. 

There are no towns or cities of any importance in Arapahoe, besides Denver; but comfortable farm houses are abundant throughout the cultivated regions, and good wagon roads traverse every section. Besides these, the iron track of the Denver and Kansas Pacific railways traverse a considerable portion of the county, and pass through thousands of acres of excellent farm lands, still awaiting the plow of the agriculturists, and ready to yield abundant wealth to all who may take advantage of their unusual fertility. Arapahoe county wants and offers, peculiar advantages to industrious farmers, and can safely insure such comfort and competency.

On August 25, 1855, the Kansas Territorial Legislature created a huge Arapahoe County to govern the entire western portion of the Territory of Kansas. The county was named for the Arapaho Nation of Native Americans that lived in the region.

In July 1858, gold was discovered along the South Platte River in Arapahoe County (in present day Englewood). This discovery precipitated the Pike's Peak Gold Rush. Many residents of the mining region felt disconnected from the remote territorial governments of Kansas and Nebraska, so they voted to form their own Territory of Jefferson on October 24, 1859. The following month, the Jefferson Territorial Legislature organized 12 counties for the new territory, including a new Arapahoe County. Denver City served as the county seat of Arapahoe County. 

The Jefferson Territory never received federal sanction, but on February 28, 1861, U.S. President James Buchanan signed an act organizing the Territory of Colorado.  On November 1, 1861, the Colorado General Assembly organized the 17 original counties of Colorado including a new Arapahoe County. Arapahoe County originally stretched from the line of present-day Sheridan Boulevard 160 miles (258 kilometers) east to the Kansas state border, and from the line of present-day County Line Road 30 miles (48 kilometers) north to the Parallel 40° North (168th Avenue). Denver City served as the county seat of Arapahoe County until 1902.  

In 1901, the Colorado General Assembly voted to split Arapahoe County into three parts: a new consolidated City and County of Denver, a new Adams County, and the remainder of the Arapahoe County to be named South Arapahoe County.  A ruling by the Colorado Supreme Court, subsequent legislation, and a referendum delyed the reorganization until November 15, 1902.  Governor James Bradley Orman designatd Littleton as the temporary county seat of South Arapahoe County.  On April 11, 1903, the Colorado General Assembly changed the name of South Arapahoe County back to Arapahoe County.  On November 8 1904, Arapahoe County voters chose Littleton over Englewood by a vote of 1310 to 829 to be the permanent county seat. 

---Wikipedia

Surrounding Counties:  Adams | Denver | Douglas | Elbert | Jefferson | Washington