Millbrook Plantation includes numerous parcels of land, a small percentage of which served for small-scale agricultural purposes in the mid-19th century. Other parts of Millbrook include Cattell Bluff, the Retreat and Elliott Lands, and Shackleford Plantation. Cattell Bluff was home to a prominent family throughout the 18th century and until the plantation was sold in 1859. In the 19th century, the land was subdivided and sold to several families, and various leases were executed for agricultural pursuits, phosphate mining, and timbering.
On the north side of Ashley River Road, Millbrook Plantation is represented by many structures and sites. From the 17th and 18th century inhabitants, the site features the ruins of the 17th century Cattell plantation house, a similar brick dependency, and the Cattell and Hanahan family cemetery. Tidal rice fields also date to the late 18th century. The area’s phosphate mining industry is visible in an 1870 company clubhouse, a tram road, and remnants of the 19th century phosphate washers along the river. 20th century developments are evident in an individual government-issue gravestone of a Civil War soldier who later resided on the land and a residence constructed by Thomas Carter in 1938. This house, modified in a Colonial Revival style in 1953, is accompanied by an early 20th century cottage and a garage.
Many structures also exist on the south side of Ashley River Road, including many residences. The Porter House was constructed in 1925 by a member of the Hanahan family, while the Summer House is located on the northeastern edge of Millbrook Plantation and dates to 1870 . A wood-framed structure in the northern section of the plantation, known as Peter Hanahan’s House, originates from 1900. Two small duplex structures date to the early 20th century and were likely used to house employees or tenants on the plantation. A small wood-frame cabin is attributed to the late 19th century and is located near the intersection of Ashley River Road and ferry Road. Millbrook Plantation is also home to many house sites, such as the Jane Richardson site from 1860 and the Sophia Singleton settlement site from the late 19th century. The W. Cattell/Seven Chimneys site, consisting of seven chimneys and three house foundations, likely represents a slave village from the late 18th century. The 1910 Olive Branch Church is represented by a site in the northern section of the plantation, and a late 19th century store lies in a cleared hunting field along Pineland Road. On the plantation’s eastern edge, there is a site known as the W. Cattell/T. Williams ruins, marked by two collapsed barns. From the 20th century, the still-active Middleton Hunt Club dates to 1908. Numerous roads remain from the 19th century, including the Porter House Road, Jerry Hill Road, Ferry Road, and three tram roads.