The former Lincoln High School has been an important educational, social, and civic landmark for the local African American community since it was established in 1937. Listed on the National Register of Historic Places, it operated from 1937 to 1969 and now serves as a community gathering place for civic and social functions. The building represents a brief period when white South Carolinians who hoped to forestall racial integration supported better facilities for Black students after Black leaders pointed out that the doctrine of separate but equal implied that segregation was only legal if school facilities were equal. While the era of explicit segregation may seem distant, this former school is one of many public schools created prior to Brown v. Board that are now home to community organizations. The building was added to the National Register of Historic Places in 2015.

The old Carnegie Public Library was the city's first and only public library in Sumter from 1917, when it was built, to 1968 when a new library opened. Though relatively small and apparently vacant as of mid-2021, it remains an important landmark in Sumter. It was one of the thousands of libraries built around the county using funds donated from philanthropist and steel magnate Andrew Carnegie. Local architects Herbert Johnson and N. Gaillard Walker designed the building in the Beaux-Arts style. The building was added to the National Register of Historic Places in 1994 and served as the headquarters of the Sumter County Library and the local genealogical society for many years.

Temple Sinai was built in 1912, replacing a wooden structure constructed around 1900. It belongs to the Congregation Sinai, whose official name is the Sumter Society of Israelites. The synagogue was designed in the Moorish Revival style. The congregation is still active and is a vital part of Sumter's Jewish community. The temple was added to the National Register of Historic Places in 1999.

The Sumter County Museum is dedicated to preserving the county's history for future generations. It is a museum complex comprised of a recreated homestead, the historic Williams-Brice House, and a garden. The house is the main museum building, featuring period rooms, a military exhibit, fine and decorative arts, and an impressive textile collection. The homestead features several buildings including a log cabin, barn, and smokehouse. Two of these buildings are original: the settler's house and commissary structures, which were built between 1812-1836. The museum acquired the Williams-Brice House when the estate donated it in 1972.

This elegant historic home was built in 1909 by prominent local farmer and businessman, Henry Lee Scarborough (1866-1929). Scarborough was also involved in the city's civic affairs, serving as Sumter County Commissioner of Public Works and in other roles. The house is one of the few surviving examples of early 20th century Classical Revival architecture in the city. It is two-stories tall and features a large porch with Corinthian columns, leaded glass in a diamond pattern directly above the entrance doors, and a small balcony above the main entrance. The house is currently occupied by a law office.

Located in the heart of downtown Sumter, the Sumter County Courthouse has served as the seat of county government since it was built in 1907. Architect William Augustus Edwards, who was from Darlington, designed it in the Beaux-Arts style. Notable features include a recessed entrance portico with six columns and arched windows, windows with pediments on the first floor, and a stone entablature surrounding the entire top of the building. The courthouse is listed on the National Register of Historic Places and is a contributing property of the Sumter Historic District, which is also listed on the Register.

Erected in 1895, the Sumter Opera House building is one of the city's best-known landmarks. It is somewhat unique in that serves as both an entertainment venue and City Hall. This dual purpose has made the building an important cultural and political center for the community. It was, in fact, the first permanent home of the city government and was also referred to as the Town Hall. The Opera House has also been the location of a meat market, barbershop, movie theater, and jail. The theater seats 500 people and hosts a variety of performances throughout the year. In terms of architecture, the building was designed in the Richardsonian Romanesque style and features a stone exterior, an attractive 100-foot-tall clock tower, and arched windows. It was added to the National Register of Historic Places in 1973.

The O'Donnell House is one of the most striking historic homes in Sumter. It was originally built around 1840 by Major John Haynsworth and his wife, Mary DeLorme, in the Italianate style. It was later renovated into its current Classical Revival appearance. It now operates as a wedding and event venue. The most notable features of the house is the semi-circular two-story porch with Corinthian columns that support an elaborate cornice. The house is named after Neill and Kate O'Donnell, who acquired it around 1900. It was added to the National Register of Historic Places in 1996.