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

The Native American interpreter Sacajawea was a valuable member of the Lewis and dark expedition in 1805.

The future survival of the bald eagle is still an important American ecological concern.

While Billie Holiday did not invent the music called "the blues", she most assuredly helped popularize it.

Eyespots,themostrudimentaryeyes,arefoundinprotozoan原生动物flagellates鞭毛虫,flatworms扁形虫,andsegmentedworms片段蠕虫.