Americans crowded around screens and packed into bars across the United States on Tuesday, some cheering and others waiting anxiously as the results of their historic election trickled in.

Barack Obama, the 47-year-old Democratic senator from Illinois, took a huge step towards becoming the first black US president, as television networks projected he would win Pennsylvania to leave McCain a razor-thin route to the presidency.

In the Finnigan`s Wake bar in the city of Philadelphia, crowds of Obama supporters roared deafeningly when his win in the state was announced, and started chanting `It`s all over.`

At one of the hottest election party tickets in the nation, 65,000 people poured in to Chicago`s Grant Park for Obama`s event, sprinting to the front for a ringside seat as history unfolds.

Up to a million more were expected to throng the streets around the lakeside park amid tight security with tens of thousands already milling around as states on the US east coast started to report their election returns.

Out west in Los Angeles, dozens of people with worried expressions gathered before outdoor television screens in Hollywood to watch results from the first eastern states to close polling.

`Calm down people! It is too early to know the truth,` said one man present, before taking out a saxophone and started to play.

From Chicago in the midwest to the Carolinas in the east and California in the west, Americans had trooped to the polls in what appeared to be record numbers to choose between Obama and Republican rival John McCain.

In Chicago, Roby Clark, a 92-year-old African-American who suffered racial slurs and harassment while serving in the army and living in the south, could hardly believe he would be able to vote for a black candidate for president.

`Through God`s blessings, I think we`re gonna get him,` Clark said as he stood outside a Baptist church on the south side of the city waiting to cast his ballot.

Even NASA astronauts got to vote in space, as turnout across the United States was reported to be heavy at the climax of the longest and most expensive presidential race in US history.

The troubled economy was the top issue for many voters in Columbus, Ohio, where Vietnam veteran McCain, 72, has been trying to make inroads with blue collar Americans.

He didn`t get the vote of Darius Thomas, 29, an unemployed construction worker. He`s supporting Obama.

`These days, no one is hiring, stores are closing, people are losing their homes and crime is rising. It`s getting worse and worse,` Thomas said.

In Blacksburg, Virginia, Norma Jean Lundis said she cast her ballot for McCain, the senator from Arizona.

`McCain stands for what I believe in -- less government, lets me control my money, the right to bear arms, life begins at conception, marriage between man and woman,` she said. `He`s a true American hero.`

Laura Burke, 46, of Lake Worth, Florida, went for Obama. `There was no way in hell I would put Sarah Palin in the presidency,` she said in a reference to McCain`s choice of running mate. If McCain wins, Palin would be the first ever female US vice president.

Crista Merrell, a 32-year-old mother of three in the Houston, Texas, suburb of Cypress, said she cast her vote for McCain and Palin because she aligned with them on moral issues.

`A lot of times we align with the Democrats on economic policy but some issues we feel strong about and that includes pro-life and how we define marriage.`

At a polling station in downtown Washington, a line stretched around the block as black, white, Latino and Asian voters, some carrying young children, waited patiently to cast their ballots.

Alnett Wooten, 86, carried an American flag with her.

`I never thought I would live long enough to do it,` she said of voting for a black president. `I just pray that He will keep him safe.`

Aboard the International Space Station, Commander Edward Michael Fincke and Flight Engineer Greg Chamitoff voted by secure electronic ballot uplinked by NASA`s Johnson Space Center Mission Control Center to the orbiting space center, NASA said.

In deep south states such as Georgia, Mississippi and Alabama, voting authorities reported record turnouts.

`I`m really into this election,` said 21-year-old shop worker Torthel McClodden in Atlanta, Georgia. `The main reason is because we have a black presidential candidate ... I never was excited about elections before.`

Florida breathed a sigh of relief as polls closed, with local and state officials saying that fears of voter irregularities and polling equipment malfunctions turned out to be largely unfounded.

`Everything went smoothly so far,` said Miami-Dade County Mayor Carlos Alvarez on Tuesday evening.