AMNA NAWAZ: Now to a new exhibition that reveals how three great 20th century painters shaped the course of their own careers while on summer retreats together.

Correspondent Jared Bowen of GBH Boston takes us to Cape Ann in Massachusetts for our arts and culture series, Canvas.

JARED BOWEN: They were three men escaping hot New York and off to chase summer at the seaside, the older seasoned painter and two young earnest ones, eager to learn from their mentor.

OLIVER BARKER, Director, Cape Ann Museum: It's about the artistic process, and it's about a friendship that was so important to three titans of American art.

JARED BOWEN: They were Milton Avery, Mark Rothko, and Adolph Gottlieb.

For successive summers in the 1930s and '40s, they came here to Cape Ann on the North Shore of Massachusetts.

In particular, they were drawn to Gloucester for its mix of natural beauty and the industrial grit of a fishing port.

It was also an artistic rite of passage, says Oliver Barker, director of the Cape Ann Museum.

OLIVER BARKER: Artists colonies were established here and is still very vibrant today.

1932 was the similar year, when the Avery invited Gottlieb and Rothko to come here.

By that point, Edward Hopper had come and gone through this city.

JARED BOWEN: The museum's new show Avery, Gottlieb & Rothko: By the Sea is the first to examine the artists' time together here.

While their New York kinship has been well-documented, this exhibition has been an excavation.

Nearly half the works have never been shown publicly, and they're a revelation, says curator Eliza Rathbone.

ELIZA RATHBONE, Chief Curator Emerita, The Phillips Collection: What's wonderful is, you can really feel them.

You're with them.

As Milton Avery's grandson said, this exhibition is as close to being there with them as we're going to get.

JARED BOWEN: So here we meet the men and the men meeting each other.

ELIZA RATHBONE: I love these two sketches by Gottlieb, one of Rothko and one of Avery, because he absolutely captures them doing what they love to do.

Rothko was a natural musician.

Gottlieb has Milton sketching because Avery was always sketching.

JARED BOWEN: Rothko described this as a golden time.

There was no rivalry.

ELIZA RATHBONE: Rothko said something wonderful later on, and maybe towards the end of his life.

He said, when we were young starting out, there were no galleries, there were no dealers, there were no collectors.

He said, we had nothing to lose and a vision to gain.

JARED BOWEN: Avery at 47 was 18 years older than the younger artists and had been coming to Cape Ann since the 1920s.

A decade later, Rothko and Gottlieb literally followed in his footsteps.

Here on holiday and far away from the grit of their New York lives and studios, they would regularly set out in the morning side by side to sketch or paint.

There was no imitation, but plenty of conversation.

ELIZA RATHBONE: We know they certainly got together every evening, pretty much, in the summertime.

They all share the same subjects, but they treat them differently.

JARED BOWEN: Including the wharves, the fishing, and of course, the beach, where Rathbone says Avery instilled in Rothko and Gottlieb the confidence to strip away the inessential.

In his watercolors, Rothko went even further, his bathers, like Cezanne before him, bask on a more ethereal beach.

ELIZA RATHBONE: There's a kind of intimacy which is perhaps unexpected.

And how does he do that?

How does he express so much feeling in works that are so spare?

JARED BOWEN: Whether Avery was painting the blazing beach sun or the Gloucester Harbor at night, reunited here for the first time with a study Rathbone discovered in Rothko's own collection, his artistic voice as the elder statesman remained consistent.

But the younger men evolved over the summers.

Gottlieb tread into seaside surrealism.

ELIZA RATHBONE: We have a series of these paintings of boxes on the beach that Gottlieb did where he puts these unrelated objects into the sections of the box.

And there's definitely a lot of surrealism in the ideas that lie behind these paintings.

JARED BOWEN: By the 1940s, Rothko's works also changed.

He began taking more wild, expressive turns, rooted in his appreciation for Greek mythology and the writings of Carl Jung and T.S.

Eliot.

As the younger men marched toward abstract expressionism, Avery's work settled into great studies of spareness.

The show ends in a gallery that doubles as a temple to these titans, a room filled with monumental late career work, the canvases that would solidify the legacy of each.

ELIZA RATHBONE: I'm just bowled over by the beauty of this room.

It almost makes me want to weep.

There's a peacefulness here and a kind of sense of fulfillment of all those very hardworking years that they spent, but years when they had nothing and came to the full realization of what they were about.

JARED BOWEN: Years when time by the ocean offered a break from regular life, where the was joy, and where a mentor delighted in encouraging his younger friends to take up the mantle of American art.

OLIVER BARKER: There's a wonderful statement that Mark Rothko made as a eulogy of sorts at the passing of Milton Avery in 1965.

He speaks about Milton Avery as a true poet, a poet that has withstood many different transitions and changes in fashion.

And, to me, there's a timelessness in that gallery.

JARED BOWEN: Where we now see how many a day at the beach helped change the tide of artistic ascent.

For the "PBS News Hour," I'm Jared Bowen in Gloucester, Massachusetts.