William A. Pinkerton with Railroad Special Agents Pat Connell (left) and Sam Finley (right)

William Allan Pinkerton (1846 - 1923) was the son and oldest child of Allan Pinkerton the founder of the Pinkerton Detective Agency. William along with his brother Robert took over the Pinkerton Detective agency after their father's health declined. Library of Congress Prints and Photographs Division, LC-DIG-ppmsca-10781