Which new form of communication put the Pony Express out of business after just 18 months of operation?

A.

carrier pigeons

B.

telegraph

C.

telephone

D.

signal flags

The use of Telegraphs made the Pony Express out of business. This is a form of mail delivery over a long distance with the use of signals and electrical connection. With the invention of the transcontinental telegraphs, the need for horsemen delivering mails are no longer needed which made the company financially troubled and collapsed.