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/H15/RIFSRP_F02_N.D, is available at:
http://www.federalreserve.gov/datadownload/Output.aspx?rel=H15&series=e048853c9a3f0734b8538f508828f298&lastObs=&from=&to=&filetype=csv&label=include&layout=seriescolumn