original_query: What was the significance of the Act of Uniformity in 1549?
query: What was the significance of the Act of Uniformity of 1549 in relation to the Prayer Book Rebellion?
answer: The Act of Uniformity of 1549 made it illegal to use the Latin liturgical rites from Whitsunday 1549 onwards, enforcing the use of the new English Book of Common Prayer.  This enforcement was a major trigger for the Prayer Book Rebellion, as it was unpopular, particularly in areas with strong Catholic loyalty, and led to violent protests and uprisings in Cornwall and Devon.