A graduate of Frederick High School, Gallaher attended Hood College in Maryland, double-majoring in both Special Education and Psychology. During his junior year, despite his love for teaching, he felt compelled to write. He switched to Goddard College on learning that David Mamet, William H. Macy, and Piers Anthony studied there. The school allowed him to create his own curriculum to major in Comics. He also taught a comics class to seniors and juniors with the work of Garth Ennis and Warren Ellis included as part of the curriculum.