1850s: Whaling is a largely unregulated business. American whalers are free to sail the open seas, and to hunt for whales in any waters.

Today: In 1986 member nations of the International Whaling Commission (IWC) vote to ban commercial whaling. Some nations, including Norway and Japan, continue to slaughter whales.

1850s: Americans continue to move west. The population of the northern states exceeds the population of the south by one million. Slaveholding states seek to expand their influence in the new territories, such as California and Utah. A compromise reached in 1850 holds the peace for a decade, but slavery becomes a major and confrontational domestic issue dividing North and South.

Today: Differences between northern and southern states remain, but not at constitutional levels. Slavery has long been abolished but many blacks suffer from racism. Foreign policy issues lead the political agenda as America seeks to...