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/RIFLGFCM01_N.WF, is available at:
http://www.federalreserve.gov/datadownload/Output.aspx?rel=H15&series=f6dcd1157b830acfd7c6047d04f525ec&lastObs=&from=&to=&filetype=csv&label=include&layout=seriescolumn