William was born in Tipperary, Ireland on March 20, 1838. He immigrated to Brantford around 1840 with his father Dennis McGrath (1798-1878), his mother Mary Walsh (1809-1896), and his five siblings. Three other siblings were born in Brantford. In the 1851 Census the entire family was listed as living in Brantford.

Interesting note: at some point William's last name was changed from McGrath to McGraw. The rest of the family kept the last name McGrath.

On December 6, 1863, he married Annie Ryan in Brantford. Annie was born in Ireland on May 1, 1841. They moved to Dunnville and then to Stratford and resided at 51 Louise Street.

William and Annie had nine children: seven daughters and two sons. Catherine (Katie) October 9, 1864March 1947), Mary Ellen (January 10,1866-June 16, 1939), William Jr., (April 1,1867-November 1,1936), Annie Loretto (August 3,1873-November 16, 1945), Margaret (Dolly)(March 29, 1874-June 2, 1962), Joseph (May 22,1874-May 19, 1918), and Jennie Gertrude (1875-1951) were all born in Dunnville, Ontario. Carrie Caroline (1879-?) and Edith (February 8, 1884-March 7, 1971) were both born in Stratford.

William was a long-time employee of the Grand Trunk Railway. He continued to work as a blacksmith until a year before his death.

At the time of his death, April 10, 1897, William was listed as living at 47 Louise Street, the same house.

The numbers of the houses changed as the lots on the street were divided to add additional residences.

After William's death Annie rented the house to Warner Heinbuck, Jennie's husband. By 1904 Alfred Vanstone, Dolly's husband, was listed as living at the house. Annie died on July 19, 1920. She was buried in Avondale Cemetery in Stratford alongside William and their infant granddaughter, Mary Heinbuck.