From Focus on Rotary Book

 Rotary’s early emblem was a simple wagon wheel (in motion with dust) representing “civilization and movement.” It was designed in 1905 by Montague M. Bear, member of the Chicago Club, who was an engraver, and most of the early clubs adopted the wheel in one form or another. Eventually, in 1922, authority was given to create and preserve an emblem for the exclusive use of all Rotarians.

Accordingly, in 1923, the present gear wheel with 24 cogs and six spokes was adopted, and a keyway added to signify that the wheel was a “worker and not an idler.” An official description of the emblem was adopted at the 1929 convention in Dallas, Texas, U.S.A. Royal blue and gold were chosen as the official Rotary colors, and the flag of Rotary was designated as a white field with the Rotary wheel emblazoned on its center. The emblem, worn as a lapel button, now identifies Rotarians around the world.