Marietta is the seat of government for Cobb County and was incorporated as a town on December 19, 1834. There are numerous stories regarding how the city received its name. Some state that Marietta was named after the wife of US Senator and Supreme Court Judge, Thomas Willis Cobb, while others contend the city is named for two legendary ladies whose Christian names were Mary and Etta. Another version claims that Marietta was named for a pioneer town in the Ohio Valley.

Marietta was one of the cities Union General William Sherman spared before going to burn Atlanta in 1864. Today Marietta is home to four National Historic Districts listed on the National Register of Historic Places.