Ken Thomasma was born in Michigan in 1930, and graduated from South High School in 1948.
From 1949 through 1950, Thomasma attended Grand Rapids Junior College before enlisting in the United States Navy. During the Korean War, Thomasma served for a year. Upon his return to Michigan, he enrolled in Calvin College in Grand Rapids; he earned his A.B. in 1953. During the summer of 1952, Thomasma had his first experience as a YMCA camp counselor: a job that he would enjoy deeply, and would eventually lead Thomasma to the West. The following summer, after graduation, Thomasma was hired as the Program Director of Camp Blodgett for inner city children.
After his summer on the shores of Lake Michigan at Camp Blodgett, Thomasma began teaching sixth grade at Mulick Park Elementary School. Five years later, in 1958, Thomasma became principal of that elementary school.
During his time in Grand Rapids, Thomasma met his future wife, Barbara. On June 16, 1955, they were married. Their son, Dan, was born in December of the following year. Thomasma returned to his position Camp Blodgett during the summers of 1956 and 1957. In 1958, after completing his Masters' Degree at the University of Michigan, Thomasma left Mulick Park Elementary and took the position of principal of Ridgeview Junior High. He stayed at Ridgeview until 1964, when he accepted a teaching position at Ken-O-Sha Elementary School.
Back in Michigan, Thomasma's career in education continued to flourish. In 1969, Thomasma left Ken-O-Sha Elementary to teach as a professor for two years at Grand Valley State College. In 1971, Thomasma accepted a different kind of position for the Grand Rapids Public Schools: Media and PR Specialist. For the next six years, which would be the family's final years in Michigan, Thomasma made and presented films and slideshows around the region. One of his most popular presentations was a travelog film about bicycling and camping across the Netherlands.
In the summer of 1973, the Thomasma family purchased one acre of land near the southern border of Grand Teton National Park in Jackson Hole, Wyoming. In 1977, the Thomasmas relocated to their newly-completed new home. Thomasma continued his career in education, but this time in Jackson Hole, Wyoming. From 1977 until 1979, Thomasma taught at the Jackson Hole Middle School. In 1979, both Ken and his wife, Barbara, began teaching at tiny Kelly Elementary School north of Jackson Hole. During his time at Kelly, Thomasma wrote his first book, Naya Nuki: Girl Who Ran. It was completed and published in 1983. In 1986, Naya Nuki was awarded the Wyoming Library Indian Paintbrush Book Award. Until 1987, Thomasma taught a combined classroom of kindergarten, first and second grades.
Since retiring from teaching, Thomasma has written nine more books: eight more titles in the Amazing Indian Children Series as well as the extremely-popular non-fiction title, The Truth About Sacajawea. During the summers of 2001 and 2002, Thomasma biked a significant portion of the Lewis and Clark Trail, from North Dakota to Oregon.
Thomasma lives in Jackson Hole with his wife, Barbara, son, Dan, daughter-in-law, Cathy and grandchildren, Melissa and Oliver.
In the summer of 1959, the Thomasma family packed a station wagon and drove nearly 2,000 miles to Lost Trail Camp in southwestern Montana. Thomasma's time at Lost Trail, a summer camp for boys, introduced him to the Lewis and Clark Expedition as well as the fascinating diversity of Indian cultures in the American West. Thomasma returned each summer for thirteen years. While all summers were full of horseback riding, mountain climbing, river rafting and backpacking, a few of them were characterized by more impressive adventures. The summer of 1966 included a 100-mile backpack traversing the Bitterroot-Selway Wilderness. For a full week in the summer of 1967, the Thomasmas tried their hand at survival camping; they backpacked into the Mt. Baker Wilderness with no supplies and lived on food they were able to hunt and gather. In 1968, Thomasma summited Mt. Rainier. During the summer of 1971, the Thomasma family spent time in Europe; after some time in the Netherlands, Thomasma, his son and wife made successful attempts on multiple peaks in the Alps including Mont Blanc and the Matterhorn.