Dhan Gopal took his ideology with him to America where he fell in with a number of dirt-poor 'anarchists' like himself. His experiences among them, in San Francisco and New York, are detailed in 'Outcast', the second section of his autobiography. In San Francisco he looked about for a way to support himself and pay for his college education, and soon lit upon writing. Around 1916 he wrote "Sandhya, Songs of Twilight" and "Rajani or Songs of the Night", two books of poems, and "Laila Majnu", a musical play in three acts, all published by Paul Elder and Co. of San Francisco. At this time, he was a student at the University of California at Berkeley for three years. Financial constraints and his political radicalism made him move on to Stanford University, from where he earned a graduate degree in metaphysics in 1914. He socialised with leftists, anarchists and freethinkers and became aware of the plight of the underclass, the white middle class, Negroes and other East Asian immigrant groups. He married Ethel Ray Dugan, an American artist and painter, in 1918, and they had a son, also called Dhan Gopal. His son popularly known as "Dan" Mukerji became one of the top officials of Pan American Airlines. He also visited Calcutta. In the 1920s, Mukerji moved to New York and began his most prolific period of writing, published mainly by E.P. Dutton. Of his many children's books, "Kari the Elephant" was the first to see publication, in 1922, followed by "Hari, the Jungle Lad" two years later and "Gay Neck, the Story of a Pigeon" in 1927. "Gay" was the most successful; Mukerji won the 1928 Newbery Medal from the American Library Association recognising it as the year's best American children's book. The story features a carrier pigeon, Gay-Neck: his training and care in the flock owned by the narrator, his drafting as a messenger for the Indian army in France during World War I, and his return to India where he and his handler deal with the wounds and memories of war in the seclusion of a lamasery. One theme is "man and winged animals as brothers". Mukerji's other children's books include "Ghond, the Hunter" (1928), "The Chief of the Herd" (1929), "Hindu Fables for Little Children" (1929), "Rama, the Hero of India" (1930, produced for the children of Dalton School where his wife taught), "The Master Monkey" (1932), and "Fierce-Face, the Story of a Tiger" (1936).