Question: Will Dockery built the 25,600 acre cotton plantation added to the National Register of Historic Places in 2006 in what state?

Context paragraphs:
Goodwood Plantation: Goodwood Plantation (also known as Old Croom Mansion) was a medium sized cotton plantation of about 1,675 acres (7 km) in central Leon County, Florida, established by Hardy Bryan Croom.  It is located at 1600 Miccosukee Road.  The plantation was added to the U.S. National Register of Historic Places on June 30, 1972.

The Forks of Cypress: The Forks of Cypress was a cotton plantation and Greek Revival plantation house near Florence in Lauderdale County, Alabama.  It was designed by architect William Nichols for James Jackson and his wife, Sally Moore Jackson.  Construction was completed in 1830.  It was the only Greek Revival house in Alabama to feature a two-story colonnade around the entire house, composed of twenty-four Ionic columns.  The name was derived from the fact that Big Cypress Creek and Little Cypress Creek border the plantation and converge near the site of the main house.  Although the main house was destroyed by fire in 1966, the site was placed on the Alabama Register of Landmarks and Heritage on April 14, 1992 and the National Register of Historic Places on October 10, 1997.  The site is the property of the State of Alabama; a local board has oversight.

Will Dockery: Will Dockery (1865–1936) built from scratch the Dockery Plantation, the famous home of such original Delta blues musicians as Charley Patton, Robert Johnson, Son House, Howlin' Wolf, Willie Brown, Tommy Johnson, and Pops Staples.

Liendo Plantation: Liendo Plantation is an historic cotton plantation in Waller County, Texas, United States.  It was added to the National Register of Historic Places on June 21, 1971.  Named for original owner José Justo Liendo, the land was sold in 1841 to Leonard Waller Groce.  In 1873, the plantation was sold to artist Elisabet Ney and her physician husband Edmund Montgomery.  Ney is buried on the grounds.

Judd Hill Cotton Gin: The Judd Hill Cotton Gin is a historic cotton gin in Judd Hill, Arkansas.  The gin was part of the Judd Hill Plantation, which was established by businessman Orange Judd Hill in the 1920s and sold to Hill's daughter and her husband, Esther and Samuel Chapin, in 1933.  The cotton gin was built on the plantation circa 1930; its brick construction, designed to prevent fires, makes it a rarity among extant cotton gins.  The plantation was successful throughout the 1940s and became one of the largest farms in Poinsett County.  The cotton gin ceased operations in the 1970s or 1980s, but the plantation is still operated by the Judd Hill Foundation established by Esther Chapin.  On September 28, 2005, the cotton gin was added to the National Register of Historic Places.

Dockery Plantation: Dockery Plantation was a 25600 acre cotton plantation and sawmill in Dockery, Mississippi, on the Sunflower River between Ruleville and Cleveland, Mississippi.  It is widely regarded as the place where Delta blues music was born.  Blues musicians resident at Dockery included Charlie Patton, Robert Johnson and Howlin' Wolf.  The property was added to the National Register of Historic Places in 2006.

Glenfield Plantation: Glenfield Plantation (originally called Glencannon) is a one-level historic antebellum home in Natchez, Mississippi.  Glenfield was built in two distinct architectural periods on a British land grant originally deeded to Henry LeFluer by King George III originally with 400 acres which grew to a 2000 acre working cotton plantation through various ownerships, circa 1774-1812 and 1845-1858.  Glenfield was declared on the National Register of Historic Places in Mississippi in 1990.

Ely-Criglar House: The Ely-Criglar House (also known as the Francis R. Ely House) is a historic site in Marianna, Florida.  It is located at 242 West Lafayette Street.  On December 27, 1972, it was added to the U.S. National Register of Historic Places.  Built by slaves from native limestone, the Greek Revival structure was completed c. 1840, as the Manor House for Francis R. Ely's 1629 acre cotton plantation.  "Ely Corner" is the site of The Battle of Marianna, where Federal troops attacked in September 1864 during The War Between The States.  Defending the town against the enemy were old men and boys, too old or too young for regular military service and those furloughed or home due to illness.

Jarrell Plantation: The Jarrell Plantation State Historic Site is a cotton plantation and state park in Juliette, Georgia, United States.  Located in the red clay hills of the Georgia piedmont, the site stands as one of the best-preserved examples of a "middle class" Southern plantation.  The Jarrell Plantation's buildings and artifacts all came from one source, the Jarrell family, who farmed the land for over 140 years.  It was added to the National Register of Historic Places in 1973.  It is a Georgia state park in Jones County.

Liberty Hill (La Grange, Georgia): Liberty Hill in La Grange, Georgia, about 0.75 mi west of the Chattahoochee River in Troup County, is a Greek Revival style plantation house built in the 1830s or 1840s.  The original cotton plantation owner, John T. Boykin, bought the piece of land the house is on in 1836.  The house with its current 150 acre property, it was listed on the National Register of Historic Places in 1975.

Supporting paragraphs: Will Dockery Dockery Plantation
Answer: Mississippi