WASHINGTON — Barack Obama was elected the nation’s first black president Tuesday night in a historic triumph that overcame racial barriers as old as America itself.

The 47-year-old Democratic senator from Illinois sealed his victory by defeating Republican Sen. John McCain in a string of wins in hardfought battleground states — Ohio, Florida, Virginia and Iowa. Final results for Indiana were not yet available.

A huge crowd thronged Grant Park in Chicago to cheer his improbable triumph and await his first public speech as president-elect.

McCain conceded shortly before 11:30 p.m.