He read law to enter the bar in 1818, and was in private practice in Charleston from then until 1831.

He was the United States Attorney for the District of South Carolina from 1831 to 1839.

[1] Gilchrist received a recess appointment from President Martin Van Buren on October 30, 1839, to a seat on the United States District Court for the District of South Carolina vacated by Judge Thomas Lee.

He was nominated to the same position by President Van Buren on January 23, 1840.

He was confirmed by the United States Senate on February 17, 1840, and received his commission the same day.