After New York, Los Angeles and Chicago, the fight is on: locals make the case for the city that should be number four.

The United States is renowned for its iconic cities. New York City undoubtedly tops the list as the nation's largest city (8.5 million residents) and one of the world's great fashion, culture and finance capitals. Los Angeles comes in just behind, the US's second-most populous city and the centre of the film industry, gateway to beaches and laid-back lifestyles. The third-largest city, Chicago, was home to the world's first skyscraper and has long vied with New York in a race to build the world's tallest, most impressive buildings.

With the top three seemingly fixed, one question recently set social media aflame: what city deserves the US's fourth spot? Residents from across the country made their case, but a few consistently rose to the top – whether by population, tourism or historical importance. We asked locals what makes their city worthy of the title and why tourists should add it to their itineraries.

This centre of federal power was purposefully built to be separate from the states and serve as the nation's capital. Named after the first president, the city sits alongside the Potomac River and still reflects its early design by Peter Charles L'Enfant, anchored by The National Mall – the central stretch of federal buildings that includes Congress, Smithsonian museums and many of the US's most famous national memorials.

Residents argue that DC deserves the "fourth city" title because of its seat of power and deep connection to history, much of which can be accessed through the free Smithsonian museums. "Washington DC has a unique focus on power, not wealth. It's not ostentatious, but discreet," said Nicolas Beliard, managing director of The Hay-Adams hotel. He also notes the welcoming nature of its residents, who tend to be open and curious about others.

The city is both walkable and accessible by its efficient Metro and bus system. "Walking around the National Mall is something I never get tired of," said resident Alyson Chadwick. "From the Capitol to the Lincoln Memorial, it is beautiful, and is super budget-friendly, with all the Smithsonian museums on the Mall and the National Zoo [a short Metro ride away] free to visit."

She recommends visitors check out the U Street Corridor for its role in shaping Black culture, from clubs where hometown jazz legend Duke Ellington performed to iconic eatery Ben's Chili's Bowl, famous for its "half-smokes" (a beef-pork sausage topped with chilli). And when Congress is in session, you might even overhear political chatter at Bullfeathers, a longtime watering hole for staffers, or at The Monocle, a Capitol Hill steakhouse.

Learn more about the best of Washington DC:

• The true story behind the US's first federal monuments

• The Washington DC sauce drenched in debate

• The mysterious sausage that even presidents can't resist

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