Robert Porter was born in Norwich, England, but was sent as a child to live with relatives in California. His first job, at age 20, was as a reporter for the Chicago Daily Inter Ocean. In 1880-81, he worked with Francis A. Walker in the preparation of reports on wealth, debt, and taxation for the 1880 census. He attracted the attention of President Chester A. Arthur, who appointed him to the Tariff Commission in 1882. From 1884-1887, he held positions on the editorial staffs of the New York Tribune and the Philadelphia Press and in 1887 was a cofounder of the New York Press.

Appointed superintendent of the 1890 census, he made extensive use of the Hollerith electrical tabulating machines and considerably increased the scope of the census. He promulgated the idea of the "end of the frontier" in the 1890 census publications, pointing out that there was no longer a discernable “frontier line” between high and low population density areas of the country.

In 1898, President McKinley appointed him special tariff and fiscal commissioner to Cuba and Puerto Rico. In 1899, at the request of the President, he induced General Maximo Gomez to disband the Cuban Army. He joined the staff of the London Times in 1904. He traveled widely and wrote extensively on a variety of social and economic topics, including a biography of President McKinley and the rise of Japan as a modern power. He was also a founder and director of the British Tabulating Machine Company. He died as a result of an automobile accident in 1917.