Few public officials have been thanked for their service on the same scale as Lord Viscount Morpeth. When he retired from his position as chief secretary for Ireland in 1841, citizens got together to send him an epic thank-you note—and today it's one of the most important documents in Irish history.

According to the video below from Great Big Story, the Morpeth Roll consists of roughly 270,000 signatures stretched out over 420 meters. When fully unfurled, the scroll—which is made from sheets that have been pasted together—is longer than the Empire State Building is tall.

Along with likely being the longest document of its kind, the Morpeth Roll also serves as a window into a specific time in Irish history. Many Irish documents from this period have been lost or destroyed due to the Great Famine and the Irish civil war. Because the scroll was kept around a spool in a box at Castle Howard in Yorkshire during Ireland's most tumultuous years, it was able to survive to the present day.

The pages have since been digitized, allowing researchers to study its contents without causing it any further damage. The 270,000 signatures have become an important resource for genealogists tracing people's Irish ancestry back to the 19th century. Even a distant relative of Prince William and Prince Harry has been found on the historic document.

[h/t Great Big Story]