Investing in stocks is one of the best ways to build wealth for retirement, but making a million from stocks by the time you retire becomes a lot easier if you buy and hold growth stocks. Granted, the volatility in growth stocks can be unnerving, but they can generate magnificent returns over time. And the earlier you start investing for retirement, the more time you have to enjoy compounding and the higher your chances of making millions.

Here are two such growth stocks that could help you retire a millionaire, thanks to their solid businesses and growth catalysts.

A tech growth stock that could grow manifold

If you had invested $20,000 inSalesforce (CRM -0.99%) 10 years ago, you'd have nearly $110,000 today. And that's after factoring in the stock's steep decline this year. The rise in Salesforce's stock price wasn't a fluke -- the company has grown its revenues and free cash flows exponentially over the years.

Salesforce is the global leader in customer relationship management (CRM), an industry that's projected to grow by double-digit compound annual growth rates in the coming years. That's not surprising given how more and more organizations want to build stronger and longer-lasting relationships with customers. CRM technology helps companies do that by managing all customer information and interactions online to improve sales. 

In 2021, Salesforce cornered 23.9% of the global CRM market. The second- and third-largest companies, SAP and Oracle, owned just about 5% market share each.

Salesforce expects its revenue to grow by roughly 20% to up to $31.8 billion in its fiscal year ending Jan. 31, 2023. By 2026, it is targeting sales worth at least $50 billion, driven largely by recent acquisitions such as the corporate messaging platform Slack. That also means Salesforce expects to almost double revenues in just four years. With that kind of growth, Salesforce shares could rise steadily over the years, making it one heck of a stock to own through retirement.

A little-known multi-bagger stock

Seemingly boring stocks can often generate market-thumping returns, and some of them even protect your capital from stock market volatility while making you money. It's a win-win combination to have in a stock that you're investing in with retirement in mind. American States Water (AWR -0.16%) is one such hidden gem that could help you retire rich.

American States Water stock's total returns (price appreciation plus dividend reinvestment) over the past decade were similar to Salesforce's, but those who started even earlier made a lot more money -- a $20,000 investment in the water stock 20 years ago would have grown 10-fold by now. There are three reasons why the stock could generate equally big, if not bigger, returns in the coming years.

First, American States Water is the largest water utility in the U.S., serving nearly 14 million customers. It's a highly regulated business that allows the company to hike tariffs periodically if approved based on its capital spending. Between 2022 and 2026, it expects such hikes to boost earnings per share (EPS) by 5% to 7% compound annual growth rates (CAGR).

Second, American States Water often relies on acquisitions to expand its footprint and expects inorganic growth to push EPS higher by up to 2.5% CAGR through 2026. The company also has a military services group that serves private military bases in the U.S. under contracts with a life as long as 50 years. Although it's a small business, it adds considerable value to the company's portfolio.

Third, American States Water is a Dividend King, and expects to increase dividends annually by 7% to 10% through 2026. Combined, its EPS and dividend growth could drive the stock significantly higher over the long term and help investors build big retirement funds.