Which means of delivering mail went out of business in 1861 after the completion of the transcontinental telegraph? C. Pony Express
The Pony Express was a mail service that delivered messages, newspapers and mail in the 1800's. This type of mail delivery was important and financially one of the greatest investments the United States has made. The Pony Express only operated for 18 months but was able to make drastic changes in a positive way from the Atlantic to the Pacific coasts.