12.27 miles; from US 6 in Woodbury to US 202 in Washington.
Route 47 was commissioned in 1932 from part of the old State Highway 154. It has seen no major changes since then; but a decrease in length of 0.15 miles since the 1940s hints at some minor realignments.
Connecticut State Highway Department. Routes and Road Numbers on the State Highway System, Showing Control Numbers and Sections. Dated Jan. 1, 1942.
Connecticut Department of Transportation. "Route change table.xls". Microsoft Excel spreadsheet file, received April 4, 2008.