http://steemreports.com/historic-steem-sbd-rates/USD
I've made a chart view which shows STEEM and SBD daily average prices on the same chart. It starts in Jan 2017, and also allows various derivatives (ratios and moving averages) to be shown by clicking on the legend at the bottom.
This is the data used for the account tools, so you can also view the data in other fiat currencies: EUR, GBP, CAD and AUD if you prefer.