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/RIFLDIY01_N.A, is available at:
http://www.federalreserve.gov/datadownload/Output.aspx?rel=H15&series=419c3e509324fc6cf296c6270bdfe394&lastObs=&from=&to=&filetype=csv&label=include&layout=seriescolumn