His father was John Whitaker (1821-1883), a successful wool merchant, and his mother was Annie Walton (1834-1921).

[2] At 16, Whitaker joined the British Army and served for 3 years with the 2nd Battalion West Riding Artillery.

To help support his family he dug ditches, built barns, and worked for $12 (equivalent to $439 in 2023) a-week as a grocery store clerk in Oakland.

At 35 years old, he started his writing career by submitting stories to the Overland Monthly and Harper's Magazine.

[3][6][2] In 1902, Whitaker and his family moved to Piedmont, California to the "Silk Culture House" at the end of Mountain Avenue.

She married Mexican-American artist Xavier Timoteo Martinez (1869–1943) in San Francisco on October 17, 1907, at age 16.

"[3][6] During this time Whitaker visited his daughter in Carmel-by-the-Sea, California where he met writer John Fleming Wilson.

At the age of 50, he was with the troops on the front lines and felt the effects of mustard gas while going "over the top" during trench warfare.

His book, Hunting the German Shark, is based on what he observed of the Allied submarine warfare in the Atlantic.

His ashes were scattered on Round Top, an extinct volcano in the Berkeley Hills, near Oakland.