Nassau Plantation was a 4,428 acres (17.92 km2; 6.919 sq mi) endeavor purchased by the Adelsverein on January 9, 1843 in Fayette County, Texas, near what is now Round Top. Designated a Recorded Texas Historic Landmark in 1968, Marker 3550.
The league of land was purchased near from what is now Round Top, from Robert Mills by Adelsverein officers Count Ludwig Joseph von Boos-Waldeck and Count Viktor August of Leiningen-Westerburg-Alt-Leiningen,at a cost of seventy-five cents an acre. It was named for the Duke of Nassau, in whose castle the Adelsverein was established. The acreage was developed as a full working plantation by slave labor bought by Count Boos-Waldeck in New Orleans, Galveston, and Houston. When Prince Solms inspected the plantation in 1844, he recommended the Verein divest itself of the property, rather than be associated with slavery.
Initially, the plantation had been considered as the primary base for arriving German immigrants, but the immigrants instead went to colonies established by Prince Carl of Solms-Braunfels and John O. Meusebach. Nassau Plantation became a luxurious noblemen's retreat for representatives of the Adelsverein. Prince Solms enjoyed horse racing and extravagant entertaining on the property.John O. Meusebach resided at Nassau from April to July 1846 to recover his health.