The new five-part documentary series “Once Upon a Time in Northern Ireland” (PBS, 9 p.m., check local listings) takes a look at the ordinary people caught up in what they called “the troubles” in Northern Ireland. It’s from the people who made “Once Upon a Time in Iraq.” The first two episodes run tonight. 

“America in Black” (BET, 8 p.m.) ends its season with a look at the March on Washington that took place 60 years ago today. 

The U.S. Open (ESPN, noon) begins early round play at the USTA Billie Jean King National Tennis Center in Queens, N.Y. 

The animated preschool series “Princess Power” (Netflix, streaming) returns for a second season.

“The Chelsea Detective” (AcornTV, streaming) returns, starring Adrian Scarborough as Detective Inspector Max Arnold, who now has a new partner.

The documentary series “Rewind the ’90s” (National Geographic 9 p.m.) concludes with a pair of episode, one showing the rise of feminism, the other showing culture disruption in that decade. 

The celebrity-adjacent reality competition show “Claim to Fame” (ABC, 8 p.m.) ends its second season and names a winner on a two hour episode.        

“Stars on Mars” (Fox, 8 p.m.) names a winner in the first season finale of the reality competition.