1908 was a big year for Curwood. He published his first and second novel The Courage of Captain Plum and The Wolf Hunter in the same year with Bobbs-Merrill publishing company and got a divorce from Cora Leon after 8 years of marriage. Their marriage had been one constructed out the romantic mind of Curwood, which produced two children, Carlotta and Viola, and ended in the non-fiction realties of life. 

After the divorce, Curwood moved back to Owosso to start a new chapter in his life. He built a home in 1909 at 508 West Williams Street. The house was originally built as a duplex with the idea that half the house could be rented out if his writing career never became successful. The front porch was blown off in the tornado that struck Owosso on 11-11-1911 at 11:11 pm. According to city folklore Curwood's family home was built on a Chippewa Indian burial ground that Chief Wasso, from whom Owosso gained its name, was buried. 

Curwood traveled to Hudson's Bay on his honeymoon and found he was creatively inspired by nature, the mountains, the wilderness, and the unknown. Over the course of his writing career, he completed many novels in the Canadian northern wilderness in cabins he often built with his own hands. Curwood lived many of the stories about which he wrote. He and Ethel Greenwood Curwood would for months bury themselves in the wilderness hundreds of miles from civilization. With wilderness as the background, his novels were infused with adventure and romance. A flavoring of the novels can be sensed, in part, by the titles, for example, Philip Steel of the Royal Mounted (Bobbs-Merrill, 1911), The Honor of the Big Snows (Bobbs-Merrill, 1911), Isobel: A Romance of the Northern Trail (Harper and Brothers, 1913) and The Valley of Silent Men (Cosmopolitan Book Corp., 1920).  

In 1914 Curwood published the novel Kazan. A story about a tame wolf-dog hybrid and written from the viewpoint of the dog, Kazan travels to the Canadian wilderness, is separated from his master and lives with a pack of wolves. Kazan sold over 500,000 copies and is often compared to Curwood's contemporary Jack London's White Fang, which was published in 1906. Curwood's story became a major motion picture in 1949 by Columbia Pictures (IMDB). 

Curwood’s success as a writer did not happen overnight. He wrote for ten years before he sold his first story, and twenty-five years before he made a comfortable living at it. His advice to authors was the same that he took for himself, “hard and steady work for years, with a fixed purpose.” 

In the same year, while Curwood was on a hunting trip in the Rockies, he saw a large bear he called Thor.  He tried to shoot him three times in three weeks.  One day as Thor approached him, he slipped and fell, breaking his gun.  The bear reared up to attack but walked away leaving Curwood untouched. The experience dramatically shaped Curwood's perspective of hunting for trophies to becoming an advocate for preserving nature. In 1916 he wrote a story from his experience called The Grizzly King which became a major motion picture called The Bear, released by RCA Columbia Pictures in 1990 (IMDB). 

Curwood described the northern wilderness areas as “God’s country.” This phrase ended up in numerous articles as well as in the titles of several novels including God’s Country and the Woman (Double-day, Page and Co., 1915), Back to God’s Country (Grosset and Dunlap, 1920), and God’s Country—Trail to Happiness (Cosmopolitan Book Corp., 1921). The latter was composed of four essays that summarized the author’s pantheistic views and feelings about nature. Curwood defined God’s country as “green forests and waters splattered with golden sun.” 

Curwood wrote about the vast wilderness of the Peace River country, the great reaches of the Athabasca and Mackenzie River districts, the solitary arctic plains, and the uninhabited forests. The Canadian government recognized the rising popularity of his stories, and hired him to explore the prairie provinces of the West and further up into the North. Curwood gathered material for articles and stories, and these, in turn, were intended to induce settlers into that country. He was the only American ever to be employed by the Canadian government as an exploratory and descriptive writer. 

Construction on Curwood Castle was started in 1922 and finished in 1923 and was an inspirational writing studio for Curwood. He composed several of his later works on a typewriter in the tower overlooking the Shiawassee River, inspired by the rushing water and his French Chateau styled castle. Today, the castle is a museum hosting exhibitions and tours and is open to the public 1pm - 5pm daily except Mondays.

Curwood was a vivid, forceful and immensely popular writer who brought the message of nature, wildlife and conservation to millions of readers. Curwood wrote, “It is my ambition to take readers with me into the heart of nature.” The out-of-doors life was for him a universal panacea. He encouraged all to partake and experience nature and enjoy all its benefits. He even believed that he would live to be a hundred years old, but his life was cut short by blood poisoning possibly caused by a spider bite. He died August 13, 1927, in Owosso, Michigan, his birthplace.

Upon his death he left behind his second wife, Ethel, who had experienced firsthand so much of what Curwood had written, and their son James Jr. along with two daughters. Curwood’s legacy lies in his writings that acted as a liaison between the masses and nature. What Curwood did, perhaps not by design but inadvertently, was to lead millions of readers a step closer to an appreciation for nature and wildlife.