Oneofthegreatestbreakthroughsforprofessionalwomencamein1973whenthefieldofbankingopenedupforthem.

The Salk vaccine is a major factor in the fight to eradicate polio.

In1861itseemedinevitablethattheSouthernstateswouldbreakawayfromtheUnion.

Despite the proliferation of other faster modes of transportation, the railroads remain the largest carriers of intercity freight in the United States.

ThefuturesurvivalofthebaldeagleisstillanimportantAmericanecologicalconcern.