Merriam attended public school in Hopkinton. He graduated from Lenox College in 1893 (his father was a trustee of the school), taught school for a year, and then returned to college to receive his Bachelor of Laws degree from the University of Iowa in 1895. He received his master's degree in 1897 and Doctor of Philosophy degree in 1900 from Columbia University. He studied in Paris and Berlin in 1899 while completing his PhD. Among his mentors from whom he adopted much of his early political thought were Frank Johnson Goodnow, Otto von Gierke, and James Harvey Robinson.