About the inspiration for these special stamps : in 1898, the PO cranked out a series of 9 stamps which were dubbed the Trans-Mississippi set,  Scott #s 285-293, a set of stamps that increasingly skyrocketed in popularity as the years --- as the decades, and even one full century, for that matter --- drifted by. The stamps, issued in denominations from 1¢ to $2.00, were a recap of some of the most monumental events in U.S. history that helped shape our great nation, west of the Mississippi River . . .

Then, exactly 100 years later, in 1998, the post office re-issued all 9 stamps on one pane of 9. The Fremont Atop the Rockies 5¢ stamp is from this eagerly sought-after set (This particular stamp is a reprint of Scott # 288, also the 5 cent variety in that vintage set.)

About the individual feature stamp, itself : this stamp spotlights Fremont raising proudly raising Old Glory atop a Rocky Mountain range.    

About the inspiration for the hand painted cachet : it was in 1843 when John Fremont climbed to the peak of the Rocky Mountains, and planted a U.S. Flag, while proclaiming that the Rockies were now a part of the United States. 

About the hand drawn and hand painted cachet : on this totally awesome, all-over cachet, we see John Fremont planting Old Glory atop the stone layered Rocky Mountains, which are accented by a placid river and stately evergreen trees below.

About the Scarcity Factor : and if the Scarcity Factor is an important consideration for you, then please note that only 10 of these potent covers were made, with this particular cover having been numbered 3/10.. 

About the cancellation and this cover comes tagged with a well-positioned bar cancel from Anaheim, California.

All in all, truly, a cover with a most commanding presence, which highlights a watershed moment in U.S. history.

INTERESTING  TIDBIT : I took this “Interesting Tidbit” from the reverse-side text of Fleetwood's 1998 Trans-Mississippi Centennial cover, which features the 5¢ John Fremont on the Rocky Mountains stamp, “A skilled explorer . . . Fremont was nominated in 1856 to be the first presidential candidate for the newly-formed Republican party, but he narrowly lost the election to James Buchanan.”