Using examples taken from the text give me a summary of why the Boston Marathon is well known.
The Boston Marathon, which began in 1897, is the world's oldest annual marathon inspired by the 1896 Summer Olympics. The Boston Marathon is one of the six World Marathon Majors. The race has been held annually since 1897 except for 2020, when the race was canceled due to the COVID-19 pandemic. The marathon is traditionally held on Patriot's Day, the third Monday of April. It attracts 500,000 spectators and 30,000 registered participants each year making it one of the most well known road racing events.