Answer:
As transportation grew
Step-by-step explanation:
Personal communication from one person to another has always been important to people. People want letters to reach the other person as soon as possible.
Mail service grew as transportation grew. The colonial post riders and circuit riders were replaced by stagecoaches. As more regular stage lines were established, mail service increased. Mail was carried from Missouri to California in twenty-five days on the stagecoach.
As more people moved to California they wanted faster mail service. In 1860 the Pony Express was started. The Pony Express rider left Missouri and rode about thirty miles to a relay station. When he arrived he tossed the saddlebags full of mail to a waiting rider who took off for the next relay station. The mail was carried to California by many different riders in about ten days. Sending a letter by Pony Express was expensive. It cost about five dollars a letter.