Waldo Clark Beals was born around 1836 in Turner, Maine, to Benjamin F. Beals and Caroline Leonard. His father was a farmer who owned $2,300 of real estate and $952 of personal property. He grew up and attended school in Turner, and he moved to Brunswick, Maine, sometime in the 1850s. By 1860, he was working as a clerk in a grocery store, and he owned $300 of personal property.
He enlisted in the Union army on October 19, 1861, and mustered in as a private in Company F of the 1st Maine Cavalry later that day. The regiment took part in the Second Battle of Bull Run, the Battle of Antietam, the Battle of Fredericksburg, the Battle of Gettysburg, and the Overland Campaign. He was promoted to corporal in 1863, and he mustered out on November 25, 1864.
Beals returned to Brunswick after the war, and he married Mary S. Owen there on September 30, 1866. They moved to Providence, Rhode Island, in the late 1860s, and by 1870, he was working as an overseer in an oil mill. A decade later, they were living in Brockton, Massachusetts, and Beals was working in a shoe shop. They moved to Auburn, Maine, sometime in the late 1800s, and by 1900, he was working as a farmer. His wife Mary died in 1903, and he married Harriet Amelia Stanwood in Brunswick, Maine, on April 28, 1905. He died of heart disease in Brunswick on May 26, 1906.