The Fitzroy River was discovered in 1837 by George Grey in the H.M.S. Beagle. The river was subsequently named by Lt J L Stokes on 26/2/1838 after the second Commander of that ship, Captain Robert FitzRoy R.N. The Fitzroy River flows for 750 km from the King Leopold and Mueller Ranges into King Sound south of Derby, and has a catchment area of 90,000 km2.

From the web at; http://en.wikipedia.org/wiki/Fitzroy_River_(Western_Australia)