Lewis Josselyn was born on August 15, 1842, in Hanover, Massachusetts, to Cyrus Josselyn and Elizabeth Bates. His father was a shoemaker who owned $1,500 of real estate and $300 of personal property in 1860. Josselyn grew up and attended school in Hanover, Massachusetts, before beginning work as a shoemaker. He enlisted in the Union army on August 12, 1862, and mustered in as a private in Company K of the 38th Massachusetts Infantry on August 20, 1862. The army stationed the regiment in Louisiana, and it took part in the Siege of Port Hudson and the Red River Campaign. The men were transferred to Virginia’s Shenandoah Valley in the summer of 1864, and they suffered significant casualties in the Battle of Cedar Creek on October 19, 1864. Josselyn mustered out on June 30, 1865, and returned home to Massachusetts.
He married Ella Frances Sampson in Hanson, Massachusetts, on December 24, 1871, and they had at least three children: Mabel, born around 1874; Gertrude, born around 1876; and Irving, born around 1877. They lived in Hanover, and Josselyn continued to work as a shoemaker. His wife Ella died in 1877, and he married Mabel Corlew on September 29, 1889. They had at least five children: Mildred, born around 1890; Leon, born around 1894; Earl, born around 1894; Clare, born around 1897; and Elva, born around 1898. Mabel died in 1933, and Josselyn followed on February 15, 1944, at the age of 101.