Any competent mathematician nowadays will agree that two is the smallest prime number, but this was not always the case. There were instances when one (or even three) was considered the smallest prime number. Two recently published papers survey the history of how prime numbers are defined: “What is the Smallest Prime?” by Chris K. Caldwell and Yeng Xiong (Journal of Integer Sequences, vol. 15 (2012), Article 12.9.7) and “The History of the Primality of One: A Selection of Sources” by Chris K. Caldwell, Angela Reddick, Yeng Xiong, and Wilfrid Keller (Journal of Integer Sequences, vol. 15 (2012), Article 12.9.8). I think these two papers will be of great use to mathematics educators.