Schwarzburg-Rudolstadt Free State of Schwarzburg-Rudolstadt Freistaat Schwarzburg-Rudolstadt Rudolstadt 1918–20 Merged into Thuringia in 1920. Schwarzburg-Sondershausen Free State of Schwarzburg-Sondershausen Freistaat Schwarzburg-Sondershausen Sondershausen 1918–20 Merged into Thuringia in 1920.