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/RIFSPPCUS_N.WF, is available at:
http://www.federalreserve.gov/datadownload/Output.aspx?rel=H15&series=4c6c9310eae5bc13434296188bdd4871&lastObs=&from=&to=&filetype=csv&label=include&layout=seriescolumn