William Pierson, associate justice of the Texas Supreme Court, the son of Marshall S. and Roxana (Ryan) Pierson, was born at Gilmer, Texas, on March 12, 1871. After the death of his mother when he was ten years old, Pierson moved with his father, a prominent banker, to Haskell, where he attended high school. He entered Baylor University in 1891 and graduated in 1896 with a degree in literature and oratory. He spent the next two years studying law at the University of Texas in Austin. After graduating in the summer of 1898, Pierson opened a law practice at Greenville, the county seat of Hunt County. Three years later he married Lena Haskell. The couple had three children, two sons, and a daughter.
Pierson was a life-long Democrat, a Baptist, a Mason, and an officeholder in the Woodmen of the World and many other civic organizations. He was elected to the Texas House in 1901 and served on the judiciary and education committees. He sponsored a bill to establish the College of Industrial Arts for Women (now Texas Woman's University) at Denton and state normal schools at Denton and San Marcos. After the completion of his term, he returned to his law practice at Greenville. In 1912 he campaigned successfully for the office of judge of the Eighth Judicial District. Pierson served as district judge for Hunt, Rains, Delta, and Hopkins counties until 1921. His decisions in seven brewery cases brought to the court by the state influenced political policymakers concerned with the controversial issue of prohibition. As a result of these decisions and his handling of other cases, Governor Pat M. Neff appointed Pierson associate justice of the state Supreme Court in 1921. Pierson was also a member of the Texas State Historical Association and served on the board of trustees of Burleson College in Greenville. He served on the bench for fourteen years. A week before his death he lamented the increasing number of cases involving violence and murder that came before the court. On April 24, 1935, William and Lena Pierson were murdered by their twenty-year-old son, Howard, the youngest of the couple's three children; Howard confessed to the crime. Family members and relatives of the young man believed that he had been emotionally unstable for a number of years. Pierson and his wife are buried in the State Cemetery in Austin.