Joseph Blau was born in Gleissenberg, Kreis Cham, Oberpfalz, Bavaria, Germany, to Michael and Barbara (Dobmeier) Blau. They emigrated from Germany in 1862 and arrived at the Port of Baltimore, Maryland on June 12, 1862. On July 7, 1862, Joseph's parents were married at St. Mary Catholic Church, Buffalo, Erie County, New York.

Sometime after Joseph's sister Mary was born (Dec. 25, 1863), the family moved to the Plain area in Sauk County, Wisconsin and purchased the former Charles Lamb farm in Franklin Township.

On November 12, 1884, Joseph married Anna Brückl (Brickl) at St. Luke Catholic Church, Plain, Sauk County, Wisconsin. Anna was a daughter of Daniel and Maria (Rötzer) Brückl, emigrants from Waldmünchen, Kreis Cham, Bavaria.

Joseph and Anna had 7 children: Albert Michael, Joseph Michael, Katharine Barbara, Simon Engelbert, Anna M., and Frank John. In 1884, Joseph bought a farm in Bear Creek Township, Sauk County, Wisconsin, located west of Plain on what was known in 2010 as Nachreiner Hollow Road.

In March 1895, they purchased a farm in Franklin Township located 2 miles north of Plain. The house was made of logs, then later was added on to and covered with siding before 1921.

Joseph's wife Anna Brueckl Blau died giving birth to their last unnamed son who also died on April 25, 1898. Son Frank, age 2, was sent to live with Mary Blau (and first husband Daniel Brueckl, 2nd husband John Ruhland, 3rd husband George Brey) with whom he lived until he reached adulthood.

Joseph soon remarried after the death of his wife, to Anna Gruber on October 5, 1898, at St. Luke Catholic Church, Plain, Sauk County, Wisconsin. Anna Gruber came into the marriage with an illegitimate 8 month old son, Albert Joseph Nachreiner. She was the daughter of Michael Gruber (an emigrant from Prosdorf, Kreis Cham, Bavaria) and Frances Ruhland (an emigrant from Untergrafenried, Kreis Cham, Bavaria).

Joseph and his second wife Anna had 4 children: Margaret Caroline, Anton Michael, George Joseph, and Clara Celia.

(Biography compiled by Debbie Blau from various sources)