“Women are the real architects of society.”

— Harriet Beecher Stowe

Annette Bening is back in Mike Mills’ emotional travelogue of the ’70s in Santa Barbara, California, and she is, as always, superb.

We like Bening because she’s real, unaffected, and can play CIA assassins as well as mobster’s girlfriends and brilliant lesbians with the same energy.

In “20th Century Women” she plays Dorothea, a crinkly 58-year-old divorcee, who chain smokes menthol cigarettes, sports Birkenstocks, dallies in the stock market, works as an industrial draftswoman and runs a kind of boarding house for the lost at the same time she is trying to keep her sweet 15-year-old son Jamie (a very good Lucas Jade Zumann) from becoming one of them.

We meet her boarders: Abbie (Greta Gerwig), a wannabe 24-year-old photographer who sports a shock of #4 blood red hair and is recovering from cervical cancer caused by a pill her mother took while Abbie was in the womb.

Despite the fact that Abbie is constantly holding onto the strings of her soul lest it fly away, and although she looks kooky, she is the wisest and most advanced thinker of the roomies. Greta, never one of my favorites, dazzles in a very soft way and impressed me with her growth.

There is the vanilla pudding blonde Julie (a splendid Elle Fanning), a 17-year-old who leaves her home at night and climbs up the brickwork to sleep with young Jamie without the blessing of sex. Sex in the film is all chatter, endless reams of it, much of it crisp, funny and imaginative, some tiresomely repetitive about female liberation and the task of ’70’s millennial women to get their stumbling male counterparts to be at ease discussing menstruation and the clitoris at dinner parties without stuttering or scaring the horses.

To liven things up, Mills throws in the live-in handyman, William (a welcome revisit with Billy Crudup), who is renovating Dorothea’s troubled Victorian house, mending, polishing and rebuilding the structure to pay his room and board. William, we learn, is a survivor of the “Summer of Love” and is serious about yoga, cabinetry and meditation.

William is a low-key stud with a knowing smile and zen calm, who sort of keeps the girls of the house on a sexual edge. There are two good scenes where William has to walk a careful line with Dorothea and Abbie, again all talk, lest he lose his lodging.

But Mills wisely keeps Willie, and in fact all of the cast, from becoming cartoon characters drifting around the ’70s. Each player is deftly drawn and given snappy lines and moments to flesh out their identities.

As in his “Beginners,” about an end-of-life, out-of-the-closet father, Mills plays the family key. This time, the subject is his mother.

We get a lot of what was truly dreadful in that era, when kids were stumbling out of the ’60s and confronting adulthood: rockers like the Clash, Talking Heads, Black Flag, and the hair curling screech of the Raincoats.

There is the not-so-funny fate of Dorothea’s aging Ford Maverick that opens the movie by bursting into flames in a parking lot.

“20th” is sort of a “six characters in search” of a plot and takes a long time blending the disparate crew of survivors and strugglers into a whole. It is, of course, Bening’s film, but her boarders are charming and often fun. A lot of credit must go to young Zumann as Jamie for moving through all the different lives and juicing them up.

J.P. Devine is a former stage and screen actor.