I'm looking to test some strategies built to react to long term changes in interest rates, corporate earnings, and inflation. I've built the infastructure and have tested SPY & TLT back to 2000's but I'd like to find assets that go further back like the SPX index and a treasury bond product.

 

I know the SPX data from S&P goes back to the 1800's; & I can find constant maturity bond index data going back to the 1960's (FRED: DGS10), but does anyone know of an index/product to use to backtest for treasuries further back than 1999? For example, TLT only goes back to about 2003.

 

Best,

 

Josh