"Once you go Mac, you just don't go back, to be honest. I just have this obsession with every product they come out with," said iPhone buyer Catherine Cardelucci.
There were two lines at the store, one for those who pre-ordered their fourth-generation iPhones about a week ago, and another line for people who hope to just walk in and get one.
"I want to have it at 7:01, I want to be first," said Carl Wilson, another iPhone buyer.
While Apple stores will be selling the new iPhones to walk-ins, AT&T stores will not.
The new iPhone is thinner with a better-resolution screen and longer battery life. It features a new operating system that can also be installed on some older models, such as the 3GS, along with cameras on both sides to permit face-to-face video calls.
"The phone just looks amazing," said Marcela Carmona outside the Pasadena store.
The iPhone craze is a worldwide phenomenon, and long lines were seen at Apple stores around the world. Some stores including ones in Tokyo and Miami sold out within hours.
At the Apple store in Tokyo's swanky Ginza shopping district, a man dressed as a giant iPhone danced and waived his arms as he made it to the front of the line. Alex Lee, 27, flew to London from Dubai to join the 500-person-long line along Regent Street.
Apple called the demand for the phone "off the charts" and said it's working hard to get phones into customers' hands as quickly as possible.
If pre-orders are any indication, this will be the most successful iPhone.
More than 600,000 people had rushed to pre-order iPhones on the first day they were available, prompting Apple and its exclusive wireless partner in the U.S., AT&T Inc., to stop taking orders for pickup or shipment by Thursday's launch. On Apple's website, new orders weren't promised for delivery until July 14.
Depending on the amount of storage, the iPhone 4 sells for $199 or $299 with a two-year contract.
The Associated Press contributed to this story.