The two-day settlement period applies to most security transactions, including stocks, bonds, municipal securities, mutual funds traded through a brokerage firm, and limited partnerships that trade on an exchange. Two-day settlement has also been the convention in the off-exchange foreign exchange market well before exchanges moved to this convention.
Government securities, stock options, and options on futures contracts settle on the next business day following the trade or T+1. Futures contracts themselves settle the day of the trade.
Why do trades of options and futures typically settle faster than trades of stocks?