The H.15 historical data is available through the Data Download Program at:
http://www.federalreserve.gov/datadownload/Build.aspx?rel=H15

This series, H15/discontinued/RIFSPPCU_N.B, is available at:
http://www.federalreserve.gov/datadownload/Output.aspx?rel=H15&series=b131f89f07a525e1f976eb2740b24074&lastObs=&from=&to=&filetype=csv&label=include&layout=seriescolumn