Of the 50 states in the United States, Pennsylvania may be the one most likely to stump grade-schoolers on a spelling test. Apparently the country's forefathers also had trouble spelling the name: On the Liberty Bell, the word Pensylvania is missing an n.

The Liberty Bell was commissioned by Speaker of the Pennsylvania Assembly Isaac Norris in 1751. It cracked on the very first test ring. (But that's not the crack everyone knows—the bell was melted down, recast, and damaged again in the 1840s). In addition to the crack, the artifact bears another, more subtle imperfection. The word Pensylvania—the bell's original and current home—is misspelled.

According to the National Science Foundation, the name as it appears on the Liberty Bell isn't necessarily a typo. Pensylvania with one n was one of several accepted spellings of the word in the 18th century. The same alternate spelling even appears in the Constitution—though the modern version with two n's is written elsewhere in the document.

Typos engraved in stone and metal are hard to fix—and more common than you may think. The Lincoln Memorial mistakenly bore the word EUTURE for years until the E was eventually changed to an F.

[h/t National Science Foundation]