Hong Kong came in first in an annual ranking of the world's most "economically free" countries, topping the chart for the 25th straight year, according to a U.S. think tank.

That's a "remarkable achievement," said Edwin Feulner, founder of The Heritage Foundation, which co-published the 2019 Index of Economic Freedom with The Wall Street Journal.

An economically free society is defined as an environment where individuals can work, produce, consume and invest in any way they please, and governments allow workers, money flows, and goods to move freely.

Hong Kong's achievement is even more impressive considering the fact that the city has come under increasing political pressure from Beijing in recent years.

As a special administrative region of China, Hong Kong operates under the "one country, two systems" framework which allows the territory to enjoy a certain degree of autonomy not seen on the mainland.

But since the pro-democracy protests of 2014, which saw tens of thousands march through the streets and paralyze parts of the financial hub for weeks, Hong Kong has seen more and more protests against Chinese interference. That's in turn prompted Beijing to harden its stance on dissent in the territory.

Hong Kong is still "clearly number one," Feulner told CNBC's Akiko Fujita on Squawk Box Monday. "It is the only country in the world that scored above 90 in our index — a 100 being perfect — and it's 90.2."

"I mean here is one country, two systems — Hong Kong number one, China 100," Feulner said, highlighting the territory's independence from the mainland.