Updated: 03/06/2015 07:09:01 AM PST

CUPERTINO — Apple’s importance to Wall Street in the past few years is nearly impossible to overstate, and the tech giant will now receive its validation by joining the Dow Jones industrial average.

Apple will replace telephone giant AT&T as one of the 30 companies in the blue-chip index, the standard-bearer for Wall Street stock indexes. It’s the first time Apple will be included in the Dow; AT&T was originally added in 1916, 20 years after Charles Dow created the index to help Americans better understand the stock market, and has been in the index for all but about a year since.

As the largest corporation in the world and a leader in technology, Apple is the clear choice for the Dow Jones industrial average, the most recognized stock market measure, David Blitzer, managing director of S&P Dow Jones Indices, said in a news release Friday morning.

Two Bay Area stock splits made Apple’s addition possible. Apple exercised a 7-for-1 stock split last year that brought its per-share price down to a level that would not have outsize sway on the stock group, and Foster City payments company Visa is scheduled to undergo a 4-for-1 split next week that will reduce the portion of the index focused on technology.

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Apple’s split brought the stock price down closer to the median price in the DJIA, Blitzer explained Friday. The Visa split will reduce the technology weight in the DJIA and make room for Apple.

Visa is also considered an information technology company by the keepers of the Dow, but Apple’s addition and Visa’s split will still bring down the weight of such companies.

Overall, the changes will reduce the weighting of information technology from 19.17 percent, down to 17.05 percent, since Visa’s 4-for-1 stock split outweighs Apple’s addition, S&P Dow Jones Indices senior index analyst Howard Silverblatt pointed out in an email Friday morning.

Apple joins four other prominent tech firms in the index: Cisco, Intel, IBM and Microsoft. Palo Alto giant Hewlett-Packard was dropped from the index in its last change, a six-company shake-up in 2013 that included Visa’s addition to the list.

Despite have the largest market cap in the world, Apple will not be the standard-bearer in the Dow due to the way prices are weighted in the index, as the stocks currently stand. The Cupertino tech giant will account for 4.7 percent of the index, the fifth largest chunk, Silverblatt revealed, trailing Goldman Sachs, IBM, 3M and Boeing.

AT&T, Apple’s exclusive partner for the first years of the iPhone, was dropped because the index had too much presence from telecomunications companies, Blitzer said. Verizon Communications will remain in the Dow to represent the sector.

Apple will officially join the index for the opening of trading on Thursday, March 19, the same day Visa expects to exercise its stock split.

Apple stock has roared to all-time highs since the company announced record corporate profits in the holiday shopping season, thanks to strong sales of new iPhones, pushing its market valuation to a U.S. record. Shares opened Friday morning at $128.40, up 1.6 percent from Thursday’s closing price.

Contact Jeremy C. Owens at 408-920-5876; follow him at Twitter.com/jowens510 .