This page visualises the yield curve of treasury securities. The real yield curve is derived from price data of inflation-protected treasuries. Although treasuries are issued by the fiscal agency, I still place this data in the Fed's section. It is a popular idea that the treasury yield is determined by market expectation of future short-term rates plus some risk premium, and the short-term rate is determined by the Fed.
The nonimal treasury yield data dates back to 1990 while the real yield data is available since 2003. Also note don't choose weekends and holidays. If you chose one date and the plot did not show up, choose another since it might be a holiday.