The 27-year-old Backes was the Blues' second-round pick in the 2003 entry draft and has 102 goals in 364 games. He tied career highs with 31 goals and 31 assists last season and scored a career-best 62 points. His plus-32 rating led NHL forwards.
Barret Jackman, Jamie Langenbrunner, Andy McDonald and Alex Steen were named assistant captains. Jackman is the longest-tenured Blues player entering his 10th season, and Langenbrunner signed a free agent deal this summer.
The Blues finished last season without a captain after trading defenseman Eric Brewer to Tampa Bay.