1) The first successful mass-produced personal computer, the IBM PC, was introduced in 1981 and played a significant role in popularizing the use of computers in homes and offices.

2) The construction of the Great Wall of China began in the 7th century BC and was completed over several centuries, spanning thousands of miles.

3) The most-watched television event in the United States is the Super Bowl, with millions of viewers tuning in each year.

4) The world's first stock exchange was established in Amsterdam in 1602.