What US dollar bill was discontinued in 1966?

US Notes were discontinued in 1966. These bills were a parallel series to Federal Reserve Notes and served no distinct purpose, so the Treasury decided it would be more economical to simply issue one type of currency.

US Notes are distinguishable by their red ink. In reality, most of them were issued as higher denominations - the last $1 US Note was dated 1928. $5 ones were printed up through the 1963 series and $100 bills up through 1966.