1901: The automobile has been invented, but few people can afford them. Under 20,000 motor cars are sold in the United States this year. Henry Ford, chief engineer for the bankrupt Detroit Automobile Company, starts his own company. He goes on to change the face of industry with his methods of mass production.

Today: Car ownership among Americans of all ages and social classes is common. Eight and a half million cars are sold in the United States each year.

1901: The president of the United States, William McKinley, is shot to death by a Polish- American anarchist.

Today: Because of the threat of assassination, the president is kept separated from the people and surrounded by security guards.

1901: Males born this year are expected to live 48.2 years. Females have a life expectancy of 51.1 years.

Today: Males born today have an average life expectancy averaging around 73 years; for...