Tom was born and raised in Mill Valley, California, on the slopes of Mt. Tamalpais. The rugged scenery of Marin County and Northern California inspired him from an early age to create landscape prints using linoleum and wood, strongly influenced by the traditional Japanese Ukiyo-ë style of Hokusai and Hiroshige. He studied History at UC Santa Cruz, where he was introduced to fine book printing by William Everson and Jack Stauffacher. In 1975, he produced his first illustrated book on UCSC's Cowell Press.
After traveling extensively in Europe and Africa, Killion returned to Santa Cruz in 1977 and founded his own Quail Press, where he published his second book, "Fortress Marin". In 1978, Killion began graduate studies in African History at Stanford University, completing a doctorate on Ethiopia in 1985. He also continued to make woodcut prints of the California landscape, producing his large-format "The Coast of California" in 1979. During the early 1980s, Tom divided his time between history research in Europe and Africa, and the development of his multi-color woodcut prints.