Brooklyn was its own city, but Queens wasn't. When NYC absorbed Brooklyn, it also took in part of Queens County, including the towns of Flushing, Jamaica, and Newtown, part of Hempstead, but not Oyster Bay.
Today it's a "borough" of NYC. Imagine that you could have a county that is smaller than a city. In county talk, Brooklyn is Kings County, NY, and the ninth biggest by population in the country, after Dallas County TX and above Riverside County CA, but maybe not for long. Brooklyn metaphorically got the stuffing kicked out when the Dodgers moved to L.A.
Deep River, CT, wow. Obscure! Missed the Philly intake cities and Williamsburg but also the one I've lived in in Boston for four decades, long ago ingested as West Roxbury. Sad!
I FORGOT TO TYPE NEW YORK! NEW FREAKIN YORK!