When William Alexander McKenzie was born on 5 April 1861, in Minnesota, United States, his father, Alexander McKenzie, was 48 and his mother, Sarah Ann Gilhousen, was 22. He married Polly May Smith on 26 May 1885, in Smithland, Woodbury, Iowa, United States. They were the parents of at least 3 sons and 1 daughter. He lived in Salubria, Washington, Idaho, United States in 1900 and Cambridge, Washington, Idaho, United States for about 20 years. He died on 31 December 1942, in Weiser, Washington, Idaho, United States, at the age of 81, and was buried in Hillcrest Cemetery, Weiser, Washington, Idaho, United States.