An American author of more than three hundred works of children's fiction, he is particularly known for his classic book, Brown Bear, Brown Bear, What Do You See?
He served in the U.S. Army Air Forces during World War II as a newspaper editor. During this period, he also published his first children's book, The Little Squeegy Bug.
He held annual workshops for children's educators, training teachers in his "Pathway to Literacy" program.
His brother, Bernard Martin, provided some of the illustrations for his children's books.
A lifelong admirer of Robert Frost, he named his Texas ranch Woodfrost in the poet's honor.