Carry On, Mr. Bowditch is a fictionalized biography that vividly recounts the life of Nathaniel Bowditch, an eminent American navigator and astronomer. Latham captures Bowditch's childhood and early adulthood, spanning from his birth in 1773 to his death in 1838. The narrative concludes with his fifth voyage, occurring when Nat is in his early thirties.

Gifted in mathematics, Bowditch aspired to attend Harvard, but his family's financial constraints made this impossible. At twelve, he was indentured for nine years to a ship chandlery in Salem, Massachusetts. Despite this, he dedicated himself to independent studies, delving into astronomy, mathematics, algebra, navigation, Latin, French, and Spanish. Local townsmen supported his efforts, granting him access to private libraries. In his early twenties, Bowditch embarked on a maritime career as a ship's clerk and second mate. He continued his studies aboard and also taught navigation to the sailors. Impressed by Bowditch's instruction, his captain famously said, "Carry on, Mr. Bowditch," endorsing his efforts. Eventually, Bowditch authored a comprehensive book on modern navigational methods, which included thoroughly revised navigation tables. This work, titled New American Practical Navigation, was published after Bowditch corrected around eight thousand errors in the previous "bible of navigation." His book remains the authoritative "seaman's bible" and is still in use today.