UnitedStates

　　officiallyUnitedStatesofAmericaFederalrepublic,NorthAmerica.

　　Itcomprises48contiguousstatesoccupyingthemid-continent,AlaskaatthenorthwesternextremeofNorthAmerica,andtheislandstateofHawaiiinthemid-PacificOcean.TheU.S.isarepublicwithtwolegislativehouses;itsheadofstateandgovernmentisthepresident.TheterritorywasoriginallyinhabitedforseveralthousandyearsbynumerousAmericanIndianpeopleswhohadprobablyemigratedfromAsia.Europeanexplorationandsettlementfromthe16thcenturybegandisplacementoftheIndians.ThefirstpermanentEuropeansettlement,bytheSpanish,wasatSaintAugustine,Fla.,in1565;theBritishsettledJamestown,Va.(1607);Plymouth,Mass.(1620);Maryland(1634);andPennsylvania(1681).TheBritishtookNewYork,NewJersey,andDelawarefromtheDutchin1664,ayearaftertheCarolinashadbeengrantedtoBritishnoblemen.TheBritishdefeatoftheFrenchin1763(seeFrenchandIndianWar)assuredBritishpoliticalcontroloverits13colonies.PoliticalunrestcausedbyBritishcolonialpolicyculminatedintheAmericanRevolution(1775–83)andtheDeclarationofIndependence(1776).TheU.S.wasfirstorganizedundertheArticlesofConfederation(1781),thenfinallyundertheConstitution(1787)asafederalrepublic.BoundariesextendedwesttotheMississippiRiver,excludingSpanishFlorida.LandacquiredfromFrancebytheLouisianaPurchase(1803)nearlydoubledthecountry'sterritory.TheU.S.foughttheWarof1812againsttheBritishandacquiredFloridafromSpainin1819.In1830itlegalizedremovalofAmericanIndianstolandswestoftheMississippiRiver.SettlementexpandedintotheFarWestinthemid-19thcentury,especiallyafterthediscoveryofgoldinCaliforniain1848(seegoldrush).VictoryintheMexicanWar(1846–48)broughttheterritoryofsevenmorefuturestates(includingCaliforniaandTexas)intoU.S.hands.ThenorthwesternboundarywasestablishedbytreatywithGreatBritainin1846.TheU.S.acquiredsouthernArizonabytheGadsdenPurchase(1853).Itsuffereddisunityduringtheconflictbetweentheslavery-basedplantationeconomyintheSouthandthefreeindustrialandagriculturaleconomyintheNorth,culminatingintheAmericanCivilWarandtheabolitionofslaveryunderthe13thAmendment.AfterReconstruction(1865–77)theU.S.experiencedrapidgrowth,urbanization,industrialdevelopment,andEuropeanimmigration.In1877itauthorizedallotmentofAmericanIndianreservationlandtoindividualtribesmen,resultinginwidespreadlossoflandtowhites.Bytheendofthe19thcentury,ithaddevelopedforeigntradeandacquiredoutlyingterritories,includingAlaska,MidwayIsland,theHawaiianIslands,thePhilippines,PuertoRico,Guam,WakeIsland,AmericanSamoa,thePanamaCanalZone,andtheVirginIslands.TheU.S.participatedinWorldWarIin1917–18.Itgrantedsuffragetowomenin1920andcitizenshiptoAmericanIndiansin1924.Thestockmarketcrashof1929ledtotheGreatDepression.TheU.S.enteredWorldWarIIaftertheJapanesebombingofPearlHarbor(Dec.7,1941).TheexplosionbytheU.S.ofanatomicbombonHiroshima(Aug.6,1945)andanotheronNagasaki(Aug.9,1945),Japan,broughtaboutJapan'ssurrender.ThereaftertheU.S.wasthemilitaryandeconomicleaderoftheWesternworld.

　　美国历史不是几句话就可以说完的,这已是压缩版,因为我是学历史的,可能觉得什么都很重要.