The Cardinals, having made up a nine-game deficit in the National League wild-card race during the month of September, became a playoff participant for the seventh time in 11 years when Atlanta fell to Philadelphia later in the evening. A victory by Atlanta against the Phillies would have brought about a one-game playoff between the Braves and Cardinals.
As the winner of the National League's wild-card berth for the second time, St. Louis will meet Philadelphia in the division series beginning Saturday. The Phillies will host the opening two games of the best-of-five confrontation.
Milwaukee will take on Arizona in the other opening-round series in the National League.
Chris Carpenter (11-9) limited the Astros to two hits and threw his second shutout of the season. It was the 15th shutout of his 15-year career.
Pujols had one of five run-scoring hits in the first inning to send the Cardinals coasting to the win over the worst team in baseball. Lance Berkman followed with an RBI single, David Freese drove in a run with a double and both Skip Schumaker and Nick Punto had RBI base hits.
St. Louis had 12 hits in the game, the last of them a solo homer by Allen Craig in the ninth. The Cardinals recorded a 90-72 record for the regular season.
Houston finished with 106 losses, the most in franchise history.
Brett Myers (7-14) allowed six runs on 10 hits in five innings to take the loss.