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/RIFLGFCM06_N.A, is available at:
http://www.federalreserve.gov/datadownload/Output.aspx?rel=H15&series=31f31a615cbd953e8d6aec3a15cc1c9b&lastObs=&from=&to=&filetype=csv&label=include&layout=seriescolumn