Shoppers hoping to be among the first to get their hands on the new iPhone 4 lined up early outside Apple’s retail stores, including the Twenty Ninth Street store in Boulder and the FlatIron Crossing store in Broomfield, Colorado.

The general line at the Boulder store began forming around 1PM, and the first customers with reservations arrived around 2PM. The line grew to about 20 people by 6PM, and by 10:30PM was over 100 people long.

The iPhone 4 line in Boulder, Colorado

Like other Apple product launch lines, people brought along their laptops and iPhones to stay occupied while they wait for the store doors to open at 7AM. One person even brought a 32-inch flat panel TV, DVD player and some movies.

The FlatIron Crossing Apple Store in Broomfield iPhone 4 line started at about 3PM, and by 11PM had grown to about 60 people. Since the store is inside a mall, the fact that people were lining up the night before the launch was surprising.

There weren’t any TVs in the Broomfield line, although someone brought their guitar to entertain the crowd. Security left a section of the mall open so customers could come inside to recharge their electronic devices — a friendly gesture that they’re trying for the first time with the iPhone 4 launch.

Near the front of the line at the FlatIron Crossing Apple Store

While the people lining up at Apple Stores will be some of the iPhone 4’s early adopters, they aren’t the first to get their hands on the combination iPod and smartphone. Customers that pre-order the iPhone 4 started receiving theirs as early as Tuesday, and more saw theirs arrive on Wednesday.

Apple and its iPhone partners began accepting pre-order sales and reservations on June 15 for the June 24 launch. Demand was substantially higher than expected, forcing Apple to push the delivery date for later pre-orders out to July 14, and AT&T along with Best Buy promptly shut down their pre-order programs.

Apple will open its doors at 7AM local time to begin processing iPhone 4 reservations.