How many years did the Pony Express mail delivery service last?
The Pony Express was in operation for just around one-and-a-half years, from April 1860 to October 1861.
Instruction: How many years did the Pony Express mail delivery service last?
Context: 
Response: The Pony Express was in operation for just around one-and-a-half years, from April 1860 to October 1861.