Question: What was Samuel Sloan's most famous building located in Natchez, Mississippi?

Context paragraphs:
Longwood (Natchez, Mississippi): Longwood, also known as Nutt's Folly, is an historic antebellum octagonal mansion located at 140 Lower Woodville Road in Natchez, Mississippi, United States.  The mansion is on the U.S. National Register of Historic Places, and is a National Historic Landmark.  Longwood is the largest octagonal house in the United States.

Politz Hebrew Academy: Politz Hebrew Academy, formerly known as William C. Jacobs School and Fayette School, is a historic school located in the Bustleton neighborhood of Philadelphia, Pennsylvania.  The building consists of an original section designed by Samuel Sloan in 1855, and the main building built in 1915.  The original building is a two-story, stone building sheathed in stucco.  The 1915 building is a 2 1/2-story, three-bay, rectangular brick building in the Colonial Revival style.  It features a hipped roof and gable dormers.

North Carolina Executive Mansion: The North Carolina Executive Mansion (also referred to as the North Carolina Governor's Mansion) is the official residence of the Governor of North Carolina and their family.  Building began in the year 1883 and it was designed by noted architects Samuel Sloan and A.G. Bauer.  The first occupants, Governor Daniel G. Fowle and his family, moved into the unfinished building in January 1891.  It is an example of Queen Anne style architecture.

Old St. Paul's Methodist Episcopal Church: Old St. Paul's Methodist Episcopal Church is a historic Methodist Episcopal church located on High Street in Odessa, New Castle County, Delaware.  It was designed by noted Philadelphia architect, Samuel Sloan and built in 1851-1852.  It is a two-story, brick building in the Greek Revival style.  It measures 45 feet by 65 feet and has a low-pitched gable roof.  The building ceased use as a church in 1955 and houses a local museum and cultural center.

Samuel Sloan (architect): Samuel Sloan (March 7, 1815 – July 19, 1884) was a Philadelphia-based architect and best-selling author of architecture books in the mid-19th century.  He specialized in Italianate villas and country houses, churches, and institutional buildings.  His most famous building—the octagonal mansion "Longwood" in Natchez, Mississippi—is unfinished; construction was abandoned during the American Civil War.

Highland Hall (Hollidaysburg, Pennsylvania): Highland Hall, also known as the Courthouse Annex, is a historic school building located at Hollidaysburg, Blair County, Pennsylvania.  It was designed by noted Philadelphia architect Samuel Sloan (1815-1884) and built about 1865.  It is a four-story, "T" shaped stone building measuring 150 feet wide and 160 feet deep.  It features a mansard roof, characteristic of the Second Empire style.  It was originally built to serve as a Presbyterian seminary for both sexes.  It became a female academy and officially named Highland Hall in 1911.  It continued to be used as a girls' school until 1940.  It became a county office building in 1969.

Sylvan Building: Sylvan Building, originally known as Central National Bank, is a historic commercial building located at Columbia, South Carolina.  It built in 1870, and is a three-story, brick Second Empire style building designed by Samuel Sloan.  It features a slate-covered mansard roof.

Lancaster County Courthouse (Pennsylvania): Lancaster County Courthouse is a historic courthouse building located at Lancaster, Lancaster County, Pennsylvania.  The original building was built between 1852 and 1855.  The original building was designed by Philadelphia architect Samuel Sloan (1815–1884).  The north wing was added between 1896 and 1898, and low flanking wings on either side of the exterior staircase were added in 1926-1927.  These later additions were designed by Lancaster architects James H. Warner and C. Emlen Urban, respectively.  It is an important example of the Romanesque Revival style.

Duell, Sloan and Pearce: Duell, Sloan and Pearce was a publishing company located in New York City.  It was founded in 1939 by C. Halliwell Duell, Samuel Sloan and Charles A. Pearce.  It initially published general fiction and non-fiction, but not westerns, light romances or children's books.  It published works by many prominent authors, including Archibald MacLeish, John O'Hara, Erskine Caldwell (including his American Folkways series) Anaïs Nin, Conrad Aiken, Wallace Stegner, E. E. Cummings, Howard Fast, Benjamin Spock and Joseph Jay Deiss.  In addition to their literary list, the firm published many works of military history with a focus on aviation in the war years.

UNC Memorial Hall: Memorial Hall was initially built in 1883 to be used for events like commencement ceremonies and the first ever basketball games at the University of North Carolina at Chapel Hill.  The architect, Samuel Sloan, designed the building to be larger than the previously used Gerrard Hall so that it could hold up to 4,000 people.  Memorial Hall was created to honor the men at the university who fought in the Civil War and to commemorate some of the important antebellum figures at the University of North Carolina.  Specifically David L. Swain was one of the men honored in the making of the building.  Funding for Memorial Hall was initially provided by selling marble tablets that were dedicated to certain men who fell in battle during the Civil War.  The tablets still exist and are kept on display at the current Memorial Hall.

Supporting paragraphs: Samuel Sloan (architect) Longwood (Natchez, Mississippi)
Answer: Longwood