What city was the first in America to adopt diagonal avenues and circles as part of its basic plan?

The city recognized for being the first in America to incorporate diagonal avenues and circles into its basic urban plan is Washington, DC. Designed by Pierre Charles L'Enfant in the 18th century, the city's layout prominently featured a series of diagonal avenues that intersected with a grid of streets, creating dynamic public spaces and ceremonial squares. This design was influenced by European urban planning ideals and aimed to represent the aspirations of the newly formed nation.

Annapolis, while historically significant, is not noted for this particular urban design innovation. Philadelphia, also important in American history, primarily features a grid layout without the diagonal avenues that characterize Washington, DC. New Amsterdam (now New York City) had its own unique system that evolved into a different urban form. Thus, the introduction of diagonal avenues and circles is a distinctive hallmark of Washington, DC's urban planning history.