The flag is unrelated to the historical flag of the town of Neuchâtel, which had been in use from 1350, and as cantonal flag from 1815 until 1848, and which remains part of the town's coat of arms. The canton of Neuchâtel was admitted to the restored Swiss Confederacy in 1815, but with the peculiar reservation that it owed nominal fealty to the king of Prussia. This lingering monarchism led to a republican coup in 1848, under the flag that would later become the cantonal flag. The conflict between monarchists by 1856 threatened to devolve into full civil war, but in 1857, Frederick William IV of Prussia renounced all claims to Neuchâtel, and the 1848 revolutionary banner was made the official cantonal flag. Use of the flag remained disputed, and during the 20th century there were three unsuccessful attempts to reintroduce the historical flag of 1350 by popular vote.