Seems like a definition of what your "tiers" are based on would provide context to what you consider a T1 city versus lower tiers. For me, it would be mostly based on population, but with elements of global relevance, history, and popular culture. The perfect example is DC - if the federal government wasn't headquartered here, it would be a T3 city at best.
T1: NYC, LA, Chicago, Houston, DC
T2: Boston, Philadelphia, Dallas, San Fran
T3: Phoenix, San Antonio, Atlanta, San Diego, Detroit, Denver, Seattle
But anyone can make an argument for other cities to be included or for these cities to be in a different tier.
that is such a dumb point. as the capitol of the country in a central location between north and south there would undoubtedly be a draw. what's the draw to philly that dc doesn't have?