One day this month an immigrant will arrive or, more likely, a baby will be born who will make the United States a nation of 300 million. This demographic milestone has prompted hand‐​ringing among environmentalists on the left and immigration opponents on the right, all of whom are misguided. Passing the 300 million mark should be cause for celebration: Never in the history of mankind have so many people lived such free and prosperous lives in one country.

Anti‐​immigration activists blame newcomers for driving up the population, when in fact most growth is natural. Since 2000, births have averaged 4.05 million a year, and deaths 2.43 million, for an increase of 1.62 million a year. Net immigration (legal and illegal) accounts for another 1.25 million a year, or 43 percent of our population growth.

Immigrants are also blamed for traffic congestion, crowded schools and suburban sprawl in certain states and metropolitan areas. But immigration on average has accounted for only 30 percent of the change in individual state populations since 2000. The biggest driver, again, has been natural growth, which accounts for 40 percent of the growth of the typical state, with the remaining 30 percent driven by migration of Americans from one state to another.

A rising population is entirely consistent with a higher quality of life. Though our population today is four times larger than it was a century ago, we live much longer and better than we did in 1906. Life expectancy at birth has grown from 48 to 78 years, infant mortality rates have plunged, a host of deadly diseases have been conquered, and the air we breathe and the water we drink are far cleaner than when we were a less populous country. Our homes, too, are much bigger, and food is more plentiful than ever. There is no reason why these trends cannot continue as the population rises.

Even at 300 million, the United States is not “overpopulated.” We remain a vast country with lots (and lots) of open space. One need only gaze out the window at 30,000 feet while flying cross‐​country to appreciate how much of America remains rural or unpopulated. We could give every American household an acre of land and still fit all 300 million of us in the states of Illinois, Iowa, and Missouri—with the rest of the country set aside as one giant national park.

Nor is the United States suffering a “population explosion.” In fact, our nation’s population growth has been slowing in recent decades. Since 1900, population has grown at an average annual rate of 1.31 percent. But in the past 15 years, the growth rate has slowed to 1.16 percent, and since 2000 the rate has slipped to just below 1 percent. Immigrants help America maintain a steady rate of growth.

Population growth does not require bigger government and higher taxes, either. Paying for roads, schools, and medical care are problems today not because we have too many people, but because the government is so heavily involved in providing those services. Notice we never worry about who will pay for the new houses, grocery stores, gas stations, and shopping malls that accompany a growing population. The market supplies those goods and services, efficiently and abundantly, and we eagerly pay for what we get.

Market reforms in health care, education, and transportation would do more to shift the burden away from taxpayers than any misguided efforts to control population growth. And a growing population actually reduces the cost to each individual for national defense and interest on the public debt.

As it has in every previous era, an expanding population confers real blessings on our country. America is unique in the world for its combination of size and wealth. A rising population combined with high productivity per worker magnifies our weight in the global economy and our influence in the world. A larger population creates a larger domestic market, spurring innovation and dynamism, and honing U.S. producers to compete and prosper in the global economy. In contrast, Western Europe, Japan, and Russia face the far more sobering prospect of a demographic implosion.

It would be a gigantic mistake for policymakers to seek to curb birth rates or immigration in a misguided effort to dampen our population growth. As long as America remains the land of the free, a growing population will mean more opportunity and more prosperity for those of us fortunate to count ourselves among the 300 million.