sentences:  At about the same time, Robert Campbell, coming from Fort Simpson explored a large part of the southern Yukon and established Fort Frances (1842) on Frances Lake in the Liard River basin and Fort Selkirk, Yukon (1848) at the juncture of the Yukon River and the Pelly River.In 1852, Fort Selkirk was sacked by Tlingit warriors from the coast who objected to its interference with their trade.Fort Selkirk was abandoned and not reestablished until 1889.