Apple Inc.has reached the other side of the hill.

The company, formed by Steve Jobs, Steve Wozniak and Ronald Wayne on April 1, 1976, turned 40 on Friday. Wall Street celebrated in a restrained manner, sending Apple shares up 0.9% to $109.99, the stock’s highest closing level since Dec. 16, 2015.

It has been an up-and-down four decades for the company, with Apple AAPL, -3.17% struggling through an identity crisis in the late 1980s and then emerging reinvigorated, surging in the years since the introduction of the iPhone in the late 2000s toward its current status as the world’s most valuable company.

From the archive:Steve Jobs named MarketWatch CEO of the Decade in 2011

As it enters middle age, Apple is once again suffering an identity crisis as it struggles to innovate beyond mobile phones and finds itself in an increasingly competitive marketplace. The company is at risk for its first year-over-year decline in iPhone sales in the current fiscal quarter.

See:Fitbit Blaze outsells Apple Watch on Amazon.com

But the company has held on to a dominating valuation, even with shares down 11.5% from 12 months ago, underperforming the 0.6% increase of the Dow Jones Industrial Average (of which Apple became a member a bit over a year ago). Apple’s market capitalization of $604.3 billion puts it ahead of rivals Alphabet Inc. GOOGL, -2.41% , valued at $519 billion, and Microsoft Corp. MSFT, -1.24% , at $437 billion.

The Cupertino, Calif., company has been criticized for a lack of innovation since Jobs died in 2011, but analysts are optimistic the introduction of the iPhone 7 later this year will help reinvigorate sales.

Earlier this week, Cowen analyst Timothy Arcuri said he believes iPhone estimates have finally bottomed after months of reductions, and that the stock is poised to rocket to $135 within the year.