Seymour Dunn was responsible for laying out many golf courses, particularly in continental Europe and (after emigrating) in New York state. His best known work includes, but is not limited to:

BELGIUM: Royal Ardenne (1900) / Royal Belgique, Ravenstein (1905) / Royal Ostend (1903).

UNITED STATES: Craig Wood G&CC, NY (1926) / Lake Placid, NY (1909, Links course) / Locust Hill CC, NY (1927) / Saranac Inn G&CC, NY (1910, with his uncle Willie Dunn Jr) / Ticonderoga GC, NY (1929) / Tuscarora CC, NY (1923).

According to his birth certificate Seymour Dunn was born on the West Links, North Berwick. As the only building on the golf course was his father Tom's club makers workshop, the assumption is that he was born in the timber building beside the first tee. Described as 5'11", with fair hair, blue eyes, and a thistle tattooed on his forearm, Seymour was 15 years old when he first visited the USA in 1897. During that visit he laid out a nine-hole course at Lawrenceville School in New Jersey.

In 1899 Seymour became the golf professional at the Societe Golf de Paris, and during this time laid out several courses in continental Europe, not least three of the Belgian "Royals," a course for King Emmanuel of Italy and one in the Rothschild Estate, France. In 1904 Seymour was pro at Royal County Down GC in Nothern Ireland, and in 1906 spent the summer at Lake Placid, New York, an area he would be associated with for much of his career.

He permanently emigrated to the USA in 1907, joining his uncle Willie Dunn Jr at Van Cortlandt Park GC, and subsequently becoming the pro at the Wykagyl GC, Rochelle, NY. Seymour set up a mail order company distributing golf equipment, while also making his reputation as a leading golf instructor of the time. He wrote the best-selling "Golf Fundamentals - Orthodoxy Of Style," with top professionals like Jim Barnes, Walter Hagen and Gene Sarazen benefitting from his personal instruction. Ben Hogan later acknowledged Dunn's swing theories in his own book "The Modern Fundamentals." In 1929 Seymour set up an Indoor Golf School in Madison Square Gardens with thirty instructors and eighteen pitch and putt holes. His contribution to the evolution of the game continues to be acknowledged.