INVESCO FIELD -- Any army of volunteers and staff is pouring into Invesco Field today, preparing for Barack Obama’s historic speech as the first African-American to accept the U.S. presidential nomination.

Just getting to the Denver Broncos home field is requiring a military-style human transportation effort, because cars are not allowed to park in the stadium parking lots for security reasons.

Crowds are already building at downtown bus stops this morning. RTD is also providing shuttle buses for people who pay to park at Coors Field, starting at 11 a.m. Light-rail service also is available.

Invesco volunteers were taking shuttle buses from Coors Field to a staging area under a freeway overpass east of Interstate 25.

Then it’s a relatively short hike under I-25 over a Platte River foot bridge to Invesco.

“Keep on going. Only two miles to go,” a security official joked as people neared the stadium

“Holey smoley!” one onlooker said as he arrived at the staging area where throngs of volunteers were lining up for their security credentials.

Be careful what you try to bring to Invesco.

At airport-like security checkpoints – staffed by federal Transportation Security Administration officers – people are told to dump any liquids outside (they can keep their bottle and refill it inside).

Officers were also confiscating fruit, the sticks from small American flags (the stickless flag can go in). Noisemakers and signs are also banned.

Security lines were moving swiftly early.

Inside sunny Invesco Field, drums and keyboards filled the air as crooning singers tested the sound system.

Stevie Wonder warmed up by playing jazzy harmonica version of "God Bless America."

People whooped when he finished.

Wonder, shown on the jumbo TV screens, is now singing a new original tune, backed by a full band.

Workers were putting the final touches on a huge blue-carpeted stage with runways that stretch out to the west-side stands.

Delegates will sit in black chairs set on white plastic mats covering the grass field.

In all, more than 75,000 people are expected to attend.