On December 1961, ninety-two-year-old architect William Welles Bosworth (1869-1966) recalled in a short memoir how he first made the acquaintance, in 1906, of the philanthropist and heir to the Standard Oil fortune, John D. Rockefeller Jr. (1874-1960). "I first met the Rockefellers when I had an apartment which adjoined that of my great friends Adele and Albert Herter in the Gibson Studio Building in New York. Late one afternoon, Mrs. Herter knocked on my door and asked if I would like to come in to tea, and meet some friends of hers who were there. I gladly obliged and spent a delightful hour in a conversation with Mr. and Mrs. John D. Rockefeller, Jr. [ ] And so it all began". Whether this first meeting was complete coincidence or a premeditated scheme, it marked the beginning of a long and fruitful professional collaboration, as well as the beginning of a sincere friendship between the two men. This report will explore a few of the several architectural projects on which Junior and Bosworth collaborated in the United States, and examine how both men benefitted from working together between 1906 and 1924, before Bosworth leaves for France to oversee restoration projects funded by Junior. It will also explain how their lifelong friendship started and why the two men got along so well.