The world's most valuable company is now a part of the Dow Jones Industrial Average, as Apple officially became a part of the index at the start of trading on Thursday.

Apple replaced AT&T on the Dow when the market closed on Wednesday, and when trading began at 9:30 a.m. on Thursday, Apple's effect on the Dow's daily performance became official.

The Dow's change became possible because of Apple's own 7-for-1 stock split, which took place in June of last year and helped to make room for the iPhone maker. Also contributing was Visa, whose 4-for-1 stock split is also effective today.

The post-split price of Visa reduced the weighting of the Information Technology sector in the index. Swapping out AT&T for Apple helped to partially offset that reduction.

AT&T had one of the lowest prices among DJIA constituents when it was decided the wireless provider would be nixed from the index. Rival Verizon remains a part of the Dow.