Was the Constellation the first pressurized airliner?

Lockheed had been working since 1937 on the L-044 Excalibur, a commercial four-engine aircraft with a pressurized cabin derived from the twin-engine Lockheed 14, and the Constellation inherited that ambition. It was designed to be the first pressurized commercial aircraft, but World War II changed the plans: the US government requisitioned production to turn it into the C-69 military transport, and the Constellation didn't enter scheduled service until February 1946.

By then a precedent already existed. The Boeing 307 Stratoliner, of which only ten were built between 1938 and 1940, was the first passenger aircraft to offer a pressurized cabin to the public. The German encyclopedia notes that the Constellation was the second long-range aircraft equipped with both a pressurized cabin and climate control, after the 307. The Spanish one adds a nuance: due to adjustments in that technology, the 307's pressurization was suspended for several months, so the Constellation was the first pressurized airliner many travelers actually experienced.

The difference in scale explains why it's often credited with first place. Ten Stratoliners barely made a mark on air transport, while the Constellation was sold to dozens of airlines around the world, from TWA and Pan American to Air France, KLM, Qantas, and Iberia. As the second commercial pressurized-cabin aircraft, it helped make air travel more affordable and comfortable for the general public. That project had taken shape in a prototype with civil registration NX 25600, which first flew on January 9, 1943, between Burbank and Muroc Field.