 About 5.10% of families and 8.10% of the population were below the poverty line, including 9.80% of those under age 18 and 7.80% of those age 65 or over.During the Third Party System, Sibley was a strongly Democratic county due to the opposition of its German Catholic populace to the pietism of the Republican Party.It voted Democratic at every presidential election until William Jennings Bryan’s Populist-backed free silver campaign drove its voters to William McKinley.