The census-designated place of Blacksville and the unincorporated communities of Flippen, Kelleytown, and Ola are located near McDonough, and addresses in those communities have McDonough postal addresses.

Named for naval officer Commodore Thomas MacDonough and founded in 1823 around a traditional town square design. The buildings surrounding the square are all intact although there are some vacancies. The county courthouse and historic jail building are on the north side near The Welcome Center in a historically maintained Standard Oil service station 1920 prototype. The station also houses the Main Street Program Office and Hospitality and Tourism Office. In the center of the square is a monument to Henry County's Confederate dead. One block east of the square, the town's original cotton warehouse has been replaced with the Henry County Judicial Center. In the same area the Henry County Courthouse Annex you can see an origial Oil on Canvas "Cotton Gin" (4½ by 11 feet) by Jean Charlot. In 1942 he painted this oil on canvas mural for the post office at McDonough, Georgia. His works can be found all over the world in everything from children's books to large murals.

The town was a relay station on the New York to New Orleans stagecoach line, and was connected by other stage lines with Fayetteville and Decatur, and with Macon by way of Jackson.

In 1900, a washout during a thunderstorm caused a train wreck about 1½ miles (2.4 km) north of town. The runoff undermined about 100 feet (30 m) of the Southern Railway (Macon division) prior the accident, and the passenger train subsequently caught fire, killing 35.

As of the census of 2000, there were 8,493 people, 3,069 households, and 2,102 families residing in the city. The population density was 1,093.8 people per square mile (422.6/km²). There were 3,234 housing units at an average density of 416.5/sq mi (160.9/km²). The racial makeup of the city was 61.4% White, 34.3% African American, 0.2% Native American, 1.4% Asian, 1.8% from other races, and 1% from two or more races. Hispanic or Latino of any race were 3.7% of the population.

There were 3,069 households out of which 35.7% had children under the age of 18 living with them, 45.2% were married couples living together, 18.8% had a female householder with no husband present, and 31.5% were non-families. 25.4% of all households were made up of individuals and 8.0% had someone living alone who was 65 years of age or older. The average household size was 2.61 and the average family size was 3.14.

In the city the population was spread out with 26.4% under the age of 18, 10.6% from 18 to 24, 34.1% from 25 to 44, 16.8% from 45 to 64, and 12.1% who were 65 years of age or older. The median age was 31 years. For every 100 females there were 90.3 males. For every 100 females age 18 and over, there were 86.1 males.

The median income for a household in the city was $41,482, and the median income for a family was $46,818. Males had a median income of $34,669 versus $28,318 for females. The per capita income for the city was $19,029. About 9.6% of families and 12.8% of the population were below the poverty line, including 13.3% of those under age 18 and 18.3% of those age 65 or over.

Although it is considered to be located in Stockbridge, many of the Eagle's Landing Country Club's homes are within McDonough's 30253 zip code.

The city of McDonough hosts an annual Geranium Festival in the springtime always the 3rd Saturday in May, celebrating the locally grown flowers and community. The one day festival serves as a showcase of local artistry and talent through the open-air craft markets and live musical performances. The Festival is sponsored by the McDonough Lions Club, and held on the McDonough Square.