Fifth Avenue was being developed with office and commercial buildings at the beginning of the 20th century.[22] By the 1920s, Fifth Avenue was the most active area for development in Midtown, and developers were starting to build north of 45th Street, which had previously been considered the boundary for profitable developments.[1]:2–3[24]:14–15[25] The most active year for construction in that decade was 1926, when thirty office buildings were constructed on Fifth Avenue.[23]:2[24]:14[26] The two-block-wide area between Fifth and Park Avenues, which represented eight percent of Manhattan's land area, contained 25% of developments that commenced between 1924 and 1926.[25]