Final answer:
Maryland is known as the 'Old Line State' for the bravery of its troops in the Revolutionary War and as the 'Free State' due to its crucial role as a border state during the Civil War.
Step-by-step explanation:
The state that is nicknamed the Old Line State or Free State is Maryland. This nickname is attributed to the state for several historical reasons. The term "Old Line" is believed to have originated from General George Washington, who referred to Maryland troops as the "Old Line" during the Revolutionary War, acknowledging their brave and steady service. Additionally, Maryland was a key Border State during the Civil War, heavily involved in the struggle between slavery and freedom, and was crucial due to its resources and strategic location. Factors such as these contributed to Maryland's reputation as a state that symbolized the tensions between North and South, ultimately leading to the nickname "Free State" as it sided with the Union.