After World War II, the Museum was reopened and operated by Poland's communist government. Amid the country's desperate economic situation, the Museum survived thanks largely to the work of Professor Marek Rostworoski, who dedicated his life to the collections. In 1991 the High Court of the Nation returned the Museum to its rightful owner, Prince Adam Karol Czartoryski, along with the library housed nearby; from 1961 the library had been located in a building at "ulica świętego Marka" (St. Mark's Street). In 1971 the Czartoryski Library was recognized as National Library.