Thomson was born near Claremont, Ontario and grew up in Leith, near Owen Sound. After moving to Toronto his early career was spent as a commercial artist. By 1911, Thomson was making regular sketching trips to areas north of Toronto and in 1912 he made the first of many trips to Algonquin Park. As well as being an artist, Thomson was an avid outdoorsman and the Park soon became his favorite place to paint. His enthusiasm for its quiet, untouched landscape with its changing moods and bright fall colors inspired other artists to explore the region. After 1914, Thomson spent most of his time painting in Algonquin, except during the coldest winter months. It was during this period that he produced the bulk of his paintings of this rugged northern landscape. Thomson painted not merely to paint, but because his nature compelled him to paint - because he had a message. The north country enthralled him, body and soul. Of all Canadian artists he was considered one of the greatest colorist. Thomson's brief but prolific career as an artist came to a premature end when he drowned mysteriously in Canoe Lake.