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.