Grier was born on March 5, 1794 in Cumberland County, Pennsylvania. At the age of 17 he enrolled in Dickinson College, where he graduated from in one year. Grier went on to teach at his fathers school, Northumberland Academy. In 1815 he succeeded his father as principal of the school. In 1817 he was admitted to the Pennsylvania bar. He practiced law until 1833, when he was appointed to State District Court of Allegheny County. In 1846 President Polk appointed Grier to the United States Supreme Court. Grier served on the Supreme Court for 23 years. He died in September 1870.