He is best known for executing large public projects in New York City and upstate, many of them a result of his long and fruitful personal relationship with Nelson Rockefeller, for whom he served as an adviser.

[4] In addition to his architectural work, Harrison served as master planner and supervising architect for a number of important Long Island-based projects, including the World's Fairs of 1939 and 1964 in Flushing, Queens, and LaGuardia and Idlewild (now John F. Kennedy) airports.

In 1931, Harrison established an 11-acre (4.5 ha) summer retreat in West Hills, New York, which was a very early example and workshop for the International Style in the United States, and a social and intellectual center of architecture, art, and politics.

Frequent visitors and guests included Nelson Rockefeller, Robert Moses, Marc Chagall, Le Corbusier, Alexander Calder, and Fernand Léger.

For example, shortly after purchasing the property in 1931, Harrison and his wife bought the Aluminaire House, an iconic, compact, ready-to-assemble steel-and-aluminum structure designed by Swiss architect Albert Frey and then editor of Architectural Record, A. Lawrence Kocher.

Léger also created a large mural for the home's circular living room and sculpted an abstract form to serve as a skylight.