In 1837 the Georgia Gazetteer reported that the city of Marietta was named for Mary Cobb, the wife of the U.S. Senator and Superior Court judge Thomas Willis Cobb. Marietta is the county seat of Cobb County, which was named for Thomas.

Although the Georgia legislature didn't legally recognized the town of Marietta until December 19, 1834, early settlers began building homes near the Cherokee town of Big Shanty (now Kennesaw) as early as 1824.

The Battle of Kennesaw Mountain was fought on June 27, 1864, when Union Maj. Gen. William T. Sherman's path was blocked by imposing fortifications on Kennesaw Mountain, near Marietta, Georgia. It was the most significant frontal assault launched by Sherman against the Confederate Army of Tennessee under Gen. Joseph E. Johnston. Although the battle ended in a tactical defeat for the Union forces, it failed to deliver the result that the Confederacy desperately needed--namely a halt to Sherman's advance on Atlanta.

The Big Chicken is a KFC restaurant in Marietta that features a 56-foot-tall (17 m) steel-sided structure designed to look like a giant chicken. Located at the city's biggest intersection of Cobb Parkway and Roswell Road, it was originally constructed in 1956. It was rebuilt following storm damage in 1993 and underwent a $2 million renovation project in 2017.

During his thirty-five-year term as president of the Brumby Chair Company, Thomas Brumby made the company one of Marietta's largest employers and one of the Southeast's largest chair factories. In fact, the company's handmade Appalachian red oak rocking chair with cane seats, known as the Brumby Rocker, was in demand nationwide, gracing porches from humble residences to the White House.

Set within the walls of Brumby Hall, which was built in 1851, the Gone With the Wind Museum evolved out of a private collection of memorabilia relating to the book by Atlanta-born author Margaret Mitchell, and the resulting 1939 film starring Vivien Leigh and Clark Gable. The museum's exhibits include the cream and black Bengaline honeymoon outfit worn by Leigh in the film, and the author's own copies of the book.

Travis Tritt was born on February 9, 1963, in Marietta, Georgia, and attended Sprayberry High School, where he founded a bluegrass group with some of his friends before going on to chart more than 40 times on the Hot Country Songs charts, including five number ones: "Help Me Hold On", "Anymore", "Can I Trust You with My Heart", "Foolish Pride", and "Best of Intentions."

In 1848, the businessman and politician John Glover arrived in Marietta. A popular figure, Glover was elected the city's first mayor when it incorporated in 1852. Although the Glovers would be successful at many business ventures through the years, their earliest successes included a tanyard and warehouse.

According to the United States Census Bureau, Marietta has a total area of 23.2 square miles (60.0 km²), of which 23.1 square miles (59.8 km²) is land and 0.077 square miles (0.2 km²), or 0.38%, is water.

After the war, two military cemeteries were opened in Marietta. Henry Greene Cole, a prominent Marietta citizen, offered land on the east side of town as a burial ground for the honored dead of both sides. When angry townspeople rejected this idea, the federal government turned the Cole property into a cemetery for Union casualties, named the Marietta National Cemetery. To the south, adjacent to the city cemetery, a private memorial association started a Confederate burial site, the Marietta Confederate Cemetery, on land donated by Jane Glover, the widow of Marietta's first mayor.