...S&P Global Ratings assigned its '###' long-term rating to Polk County, Iowa's series 2017A general obligation (GO) refunding bonds and series 2017B taxable GO refunding bonds. At the same time, we affirmed our '###' long-term rating on the county's previously rated GO bonds. The outlook is stable. The county's full-faith and credit pledge, and an agreement to levy ad valorem property taxes without limitation on the rate or amount, secure the bonds. The series 2017A bond proceeds will be used to current refund the county's outstanding debt, including that of series 2010A, B, and C for interest cost savings. Series 2017B bond proceeds will be used to current refund the county's outstanding debt, including that of series 2010A and B and 2012B, and a portion of the June 1, 2017 maturity of the GO bonds, series 2015A to extend the combined maturity to 2026 from 2023. Polk County's bonds are eligible to be rated above the sovereign because we believe the county can maintain better credit characteristics...