His philosophy was outlined in 1898 in the book, To-morrow: A Peaceful Path to Real Reform (republished in 1902 as Garden Cities of Tomorrow), in which he suggested that out of a marriage of town and country would spring "a new hope, a new life, a new civilisation". This was to use a model of community governance, an capture an uplift in land value that arose from development for the community rather than individual land owners, investing it for the long-term benefit of all.

Drawing philanthropists and idealists from far afield, Howard founded Letchworth Garden City in 1903 to breathe life into this dream. The town, and the global Garden City movement it inspired, revolutionised ideas about high quality planned towns. His experiment at Letchworth Garden City proved his model worked, and Howard's ideas were soon being shared more widely around the world.