TheNativeAmericaninterpreterSacajaweawasavaluablememberoftheLewisanddarkexpeditionin1805.

Urbanrenewalprogramsstrivetoupgradeareasthatarebecomingslums.

ThefirstimportantexpositionintheUnitedStateswasheldinPhiladelphiain1876.

ThefuturesurvivalofthebaldeagleisstillanimportantAmericanecologicalconcern.

Creamoftartar酒石,aweakacid,canbeaddedtoeggwhitestohelpthemfoam泡沫whentheyarebeaten