Here's the Smartest Way to Invest in the S&P 500 in March

The S&P 500 index is having a sluggish start to the year. So far in 2026, the popular benchmark is down almost 2% (as of March 17). Investors might be anxious about geopolitical conflict, huge artificial intelligence spending, or general economic uncertainty. These are certainly major topics.

But long-term investors have always benefited by buying during moments of weakness. If you're thinking of putting some money to work right now, here's the smartest way to invest in the S&P 500 in March.

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Keep it simple

One of the best ways to build exposure to the S&P 500 in your portfolio is to buy the Vanguard S&P 500 ETF (NYSEMKT: VOO). This exchange-traded fund is offered by the well-respected and leading asset manager Vanguard, which has been operating for five decades. The fund has $1.5 trillion in total assets, making it one of the largest such products around.

Containing 500 or so large and profitable American businesses, the S&P 500 represents about 80% of the total market cap of the U.S. stock market. It's heavily skewed to the technology sector, which represents 32% of the ETF's portfolio. This might not come as a surprise, especially since some of the world's most valuable companies operate in these industries, according to research from The Motley Fool.

Investors benefit by owning an ETF with an extremely low expense ratio of just 0.03%. That's tiny when you compare it to many of the high-priced active funds out there with poor track records against the S&P 500.

Past and future

The Vanguard S&P 500 ETF's performance is noteworthy. In the past 10 years, it would have grown a $2,000 starting investment into $7,800 today, translating to a 290% total return. These gains demonstrate just how lucrative it has been to own U.S. stocks. Now that the S&P 500 is more than 3% off its peak, it makes sense to buy during the dip.

But what kind of returns can investors expect in the future? The answer is unknown since the stock market is unpredictable. On one hand, the S&P 500's valuation shouldn't be ignored. Historical data shows that forward returns can be disappointing if starting from a position of higher prices. On the other hand, though, it's always a good idea to remain optimistic and bullish over the long term. Time in the market always beats trying to time the market.

With this fresh perspective in mind, the Vanguard S&P 500 ETF is a great portfolio addition in March.

Neil Patel has positions in Vanguard S&P 500 ETF. The Motley Fool has positions in and recommends Vanguard S&P 500 ETF. The Motley Fool has a disclosure policy.