NEW YORK TIMES, April 21, 1860  The front page has: "News By Telegraph -- California -- Arrival of the Pony Express" with the first article having a dateline of: "St. Joseph" beginning: "The Central Overland Pony Express, bringing California dates to April 10 & Carson Valley to the 11th, arrived at 5 p.m. exactly on time." Given the very short life of the Pony Express, it can be difficult to find front page mentions of it.
Eight pages, very nice condition.