Frank Seth Leffingwell (November 16, 1868 – August 6, 1945) was a businessman, stone cutter, horse trader, real estate agent, officer of the law, as well as a municipal and provincial politician who was elected to public office in both the United States and Canada.

In that election Warner had become big enough to have its own seat represented in the Legislative Assembly of Alberta.

Leffingwell was re-elected to his second term in office in the 1917 Alberta general election with a comfortable plurality.

After Conner retired in 1935 he attempted to run for office one more time in the 1935 Alberta general election.

This time he placed a distant third behind Social Credit candidate Solon Earl Low and James Walker.