Paul Charlton was born in Harrisburg, Pennsylvania on November 2, 1856. His parents were Samuel Templeton Charlton and Clare Charlton. He studied law at Yale University, where he was a classmate of William Howard Taft, who became President of the United States in 1908, and of William N. Hunt, who was Governor of Puerto Rico from 1901 to 1904. He was married on January 8, 1908, and had one son, Porter Charlton.
From 1882 to 1888 he practiced law in Harrisburg, Pennsylvania, and in Omaha, Nebraska. From 1901 to 1911, he served as Legal Counsel for the War Department's Bureau of Insular Affairs, which was responsible for the United States Government's administration of Puerto Rico and the Philippines. He was the author of the proposed legislation regarding the naturalization of the residents of the Philippines in 1906, the Compiler and Director of important Acts and Treaties related to Alaska, and found time to be a lecturer at George Washington University.
On July 1, 1911, President William Howard Taft appointed Judge Charlton to the federal bench in Puerto Rico. He served until March 26, 1913, when he resigned to practice law in San Juan. Judge Charlton died at Hospital San Lucas in Ponce on June 4, 1917, after surgery for a carbuncle.
Judge Charlton is considered to be one of the brightest minds to sit on the federal bench in Puerto Rico. He was known for his sympathy, his legal acumen and the excellent manner in which he presented his cases as an advocate.