The Liberty Bell stands as one of the great symbols of American democracy. But what makes it so special, and how did it get its famed crack?

In 1751, the Pennsylvania Provincial Assembly—part of the state’s colonial government—paid around 100 pounds for a large bell to hang in its new State House (later known as Independence Hall). Cast at London’s Whitechapel Bell Foundry, the bell arrived in Philadelphia in August 1752. Because the metal was too brittle, it cracked during a test strike and had to be recast twice.

The final version—made of 70 percent copper, 25 percent tin and small amounts of lead, zinc, arsenic, gold and silver—weighed around 2,080 pounds and measured 12 feet in circumference around the lip and 3 feet from lip to crown.

On July 8, 1776, the bell was rung to celebrate the first public reading of the Declaration of Independence. After the British invasion of Philadelphia, the bell was hidden in a church until it could be safely returned to the State House. A popular icon of the new nation and its independence, it wasn’t called the “Liberty Bell” until the 1830s, when an abolitionist group adopted it as a symbol of their own cause.

So when did the Liberty Bell get its famous crack? That’s not exactly clear.

According to one of many stories, it first cracked back in 1824, during the visit of the Revolutionary War hero Marquis de Lafayette. Another story holds that it fractured later that year, while tolling to signal a fire. One of the most popular legends claims that the bell cracked during the funeral of Chief Justice John Marshall in 1835, but newspaper accounts of the funeral do not mention such an incident.

Whatever the truth is, it seems the bell was certainly damaged by 1846, when (according to official city records) Philadelphia’s mayor requested that the bell be rung on George Washington’s birthday. Though attempts were made to repair an existing fracture in the bell for the occasion, and the bell reportedly tolled loud and clear at first, it subsequently cracked beyond repair and had to be taken out of service. After being moved to a pavilion near Independence Hall in 1976 (the bicentennial of the Declaration of Independence), in 2003 the Liberty Bell was relocated to Liberty Bell Center in Independence National Historic Park, where millions of visitors view its famous crack each year.