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/RILSPDEPM01_N.WF, is available at:
http://www.federalreserve.gov/datadownload/Output.aspx?rel=H15&series=0d5c7f6a4165dc8b257493c7b4edfe42&lastObs=&from=&to=&filetype=csv&label=include&layout=seriescolumn