Blackford County is located in the east central portion of the U.S. state of Indiana. The county is named for Judge Isaac Blackford, who was the first speaker of the Indiana General Assembly and a long-time chief justice of the Indiana Supreme Court. Created in 1838, Blackford County is divided into four townships, and its county seat is Hartford City. Two incorporated cities and one incorporated town are located within the county. The county is also the site of numerous unincorporated communities and ghost towns. Occupying only 165.58 square miles (428.9 km2), Blackford County is the fourth smallest county in Indiana. As of the 2020 census, the county's population was 12,112. Based on population, the county is the 8th smallest county of the 92 in Indiana. Although no interstate highways are located in Blackford County, three Indiana state roads cross the county, and an additional state road is located along the county's southeast border. The county has two railroad lines. A north–south route crosses the county, and intersects with a second railroad line that connects Hartford City with communities to the west.

Isaac Newton Blackford was the second Chief Justice of the Indiana Supreme Court, the court's longest serving Justice, and among the longest serving jurists in the history of the United States. He wrote an eight-volume work entitled Blackford's Reports recording all the early decisions of the court. The books became a staple legal source among Indiana's lawyers and received national and international acclaim for their style, accuracy, quality, and concision in dealing with common law. As a jurist, Blackford was the most influential ever to serve on Indiana's courts, according to former Chief Justice of Indiana Randall Shepard. He was nicknamed the "Indiana Blackstone" because of a comment made by Washington Irving regarding the popularity of Blackford's books. During his lifetime he was nationally renowned as one of the most prominent jurists in the United States.