usagov:

Image description: As a publicity stunt in the 1888 presidential campaign, supporters of Benjamin Harrison rolled a huge ball covered with campaign slogans halfway across the country. The ball was a replica of one built for Harrison&rsquo;s grandfather, William Henry Harrison, for his 1840 presidential campaign. The gimmick gave rise to the phrase, &ldquo;Keep the ball rolling.&rdquo; Learn more about this historical event.
Photo from the Prints and Photographs Division, Library of Congress

History is awesome. :D