Sharing a #26 on cover today.
The Central Overland And California & Pike's Peak Express Company, Denver City K.T. Dec 1, oval datestamp with matching "The Central Overland And California & Pike's Peak Express Company, St. Joseph. Mo. Dec 7" oval on cover to Millville, Missouri, entered the mails with "Saint Joseph Mo Dec 8" double circle datestamp tying 3c Dull red (26), few toned spots, very fine and scarce.
This marking was used between November 6, 1860 & September 12, 1861.




From Alexander's Simpsons ...
Rocky Mountain Mails and the Pony Express
The Leavenworth & Pikes Peak Express Companies
Gold was discovered at the present site of Denver in the summer of 1858, causing a great rush to the area from the East. While post offices were established at Auraria and Coraville in January and March, 1859, no through U.S. mail service was established over the Platte River Road until August, 1860.
Between 1859 and 1861 one or all of the partners of the freighting
firm of Russell , Majors & Waddell, acting through two corporations and one unincorporated association, ran express service to the mines, which included carrying mail. The postmasters at the western terminals of the regular mail system (at St. Joseph, Leavenworth, and Atchison) were directed to deliver mail for this area to those express companies.
From April 18 to July 2, 1859, the express service was operated by the Leavenworth & Pikes Peak Express Company over the Smoky Hill Route (across Kansas Territory). This company was a subsidiary of Jones & Russell Company.
On July 2, 1859, the express service was moved to the Platte River Route and operated directly by the Jones & Russell Express Company.
This company acquired the mail contract to Salt Lake City. At this time the U.S. mail route was extended to Julesburg for mail directed to the Colorado gold fields.
The last run of this service occurred on February 23, 1860.
In order to provide the necessary financial resources to extend their services to California and to inaugurate the Pony Express, Russell, Majors & Waddell organized the Central Overland & Pikes Peak Express Company on February 13, 1860, which bought out the predecessor company, and began service under the new name.
The Jones & Russell handstamp was continued in use until receipt of the new oval markings, about June 1.
New postal contracts were not awarded to the Central Overland & Pikes Peak Express Company, the Denver to Julesburg contract being awarded to E. F. Bruce in August, 1860.
On March 2, 1861 , a contract for over land mail service to California was awarded to the Butterfield Overland Mail Company.
However, an agreement was reached by these parties whereby the Central Overland & Pikes Peak Express Company actually operated both of these services east of Salt Lake City under sub-contract.
Consequently, a weekly mail service was inaugurated to Denver on August 14, 1860, though much mail continued to be carried by express.
On March 22, 1862, Ben Holladay bought the Central Overland & Pikes Peak Express Company and continued the service as the Over land Stage Line. Until September, 1860, the express charge was 25˘ per letter in addition to U. S. postage; thereafter, it was reduced to 10˘ as a result of competition with Hinckley & Company.
See also "The Leavenworth and Pikes Peak Express Companies"
by David T. Beals III
in Western Express, October, 1975, pp. 3-13.