It took the city until 2007 to recognize Crown Heights North as a historical district, but anyone wandering around the elegant row houses and mansions in the neighborhood is aware of how deserved the designation is. Get to know the nabe this weekend with the Municipal Art Society’s Saturday morning tour of Crown Heights North, led by architectural historian Matt Postal. Architectural gems like Grant Square’s former Union League Club and the LEED-certified and visually arresting Brooklyn Children’s Museum will be included on the tour, along with an in-depth exploration of the historical buildings on Dean Street.