The peace negotiations were held in the cities of MÃ 1\/4 nster and OsnabrÃ 1\/4 ck , which lie about 50 km apart from each other , in the present day German states of North Rhine-Westphalia and Lower Saxony . Sweden had favored OsnabrÃ 1\/4 ck due to its Protestant background , France chose MÃ 1\/4 nster due to its Catholic background . This larger agreement was to be negotiated in Westphalia , in the neighbouring cities of MÃ 1\/4 nster and OsnabrÃ 1\/4 ck .