Text pages are also generously illustrated with black-and-white pen-and-ink drawings, many with explanatory captions (to accompany the action of the story), in the margins.

On a spring day in the early twentieth century, a common snapping turtle (Chelydra serpentina) hatches near Little Elk Lake in Minnesota's Itasca State Park.

Soon after emergence the hatchling is hit by a stray bullet from a poacher's gun, amputating her left rear leg.

The boy decides that the three-legged hatchling will have a difficult time surviving in the competitive ecosystem of Little Elk Lake, and takes the turtle with him when he accompanies a ranger from Itasca State Park on a trip into the headwaters of the Mississippi River.

Holling explains that Minn's missing back leg means that she can't "bottom-walk" upstream against the river's current during spring floods.

"[3] The books share a distinctive non-linear format in which the printed main narrative and color illustrations are juxtaposed with elaborate marginal content.

"[6] Minn of the Mississippi received a positive review from Kirkus Reviews, which wrote, "this new lovely picture book, bursting with legend, history, natural science, convincing personalities and even a few wise saws, has such a bountiful collection of loving detail and good story, that it is bound to keep the reader happy and busy for some time.

[1] The Hollings' "art of digression" method of writing and illustrating books has inspired other creators of children's literature.

Notably, illustrator Bob Marstell and book designer Hans Teensma, who along with author Lawrence Pringle created the Orbis Pictus Award-winning ALA Notable Book An Extraordinary Life: The Story of a Monarch Butterfly (1997) identified Minn of the Mississippi as a major influence on their work.