This is the first year in which the State Quarters were introduced by the U.S. Mint. In 1999 the Mint issued five different designs, with the Pennsylvania design being the second.
Most circulation strike 1999-D Pennsylvania Quarters came in nice quality. Examples in circulated grades and up to MS64 or MS65 condition could have been pulled from circulation. Most examples in MS66 condition or higher usually came from mint sets, bags or rolls. In MS67 condition they are scarce with no more than several hundred known. In MS68 condition they are extremely scarce with less than a handful known and none being graded higher.