According to the 1900 United States census, he was born in June 1899; his age was given as 11/12.
1900 United States census, Benson, Swift County, Minnesota, population schedule, enumeration district no. 270, sheet no. 11A, family 190. Ancestry.com. 1900 United States Federal Census [database on-line]. Provo, UT, USA: Ancestry.com Operations Inc, 2004.
Walter died on 26 September 1900 in Danvers, Swift County, Minnesota. His age at death was given as 1 year, 8 months, and 14 days, which suggests that he was born on 12 January 1899. The cause of death was cholera infantum.
Swift County, Minnesota. Death card, Walter Boe, 1900. Iron Range Research Center, Chisolm, Minnesota.
John and Signe's next son, born in 1901, was also given the name Walter.