YAKIMA, Wash. — Some Yakima Valley residents hardly notice the markings on the Selah and Rattlesnake ridges.

For others, they’re landmarks highlighting a community or a school.

Near Lookout Point outside Selah, large white rocks form a large S near the top of the ridge. There’s faint evidence of other letters alongside it.

On the north slope of Yakima Ridge is a large white cross highly visible to motorists approaching Selah on Interstate 82. And further south, near Union Gap, there’s a letter L on the hillside that someone has tried to turn into a cross.

These kinds of markers go by a variety of names — hillside letters, mountain monograms — and they can demonstrate pride in a school or community or can be a symbol of religious devotion.

In some cases, they become a part of the community’s identity.

“You just know that it is Selah,” said Selah resident Norma Smith, referring to the large S above the town, put in place more than 70 years ago by high school students honoring their school.

Sometimes they create an air of mystery when their origin is lost to memory.

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Placing large letters on hillsides dates to 1905, when the University of California at Berkley installed a large C on the hill above its San Francisco Bay Area campus, according to James J. Parsons, a UC-Berkeley geography professor who has studied the history of hillside letters.

It was followed by Brigham Young University, which installed a 322-foot-tall block Y on a mountainside above Provo, Utah, in 1906.

Parsons wrote in a 1988 article for Landscape Magazine that the letters are found mostly in the western United States, where tall ridges and mountains that were unlikely to be developed made ideal canvases for such displays.

Parsons, who died in 1997, mapped about 250 such markings throughout the West, but noted his work was by no means definitive.

“The letters remain a conspicuous and durable part of the identity of many communities, fortifying institutional allegiances and the sense of place,” Parsons wrote.

While some have fallen into disrepair through the years, others are lovingly maintained.

“They’re a living, crisp addition to community social capital, and that’s good for all dwelling in a community,” said Paul Starrs, a geography professor at the University of Nevada who has written on the subject.

One online listing indicates that there are 19 such monograms throughout the state. In the Yakima Valley there are at least four — two letters, two crosses.

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The Selah S, on the ridge near Lookout Point, was created sometime in the late 1920s to 1930, with the letter carved into private land on the hillside, and a layer of stones placed at the bottom to make it stand out from the hillside.

During homecoming games, the S was filled in with wood and other combustible material by the school’s senior class and set on fire as a way to celebrate the big event.

Sharon Nicklin, Selah High School class of 1964, said her mother recalled seeing the S on the ridge burning for homecoming games in the 1930s. The S was visible from the old high school, located where the current district office stands, Nicklin said.

Nicklin, who is now Selah High School’s attendance secretary, participated in the lighting ceremony herself.

“We thought we could do better, and we used old tires (instead of wood),” Nicklin recalled. But she said one of the tires rolled down the hill and interrupted rail service in the area for a short period of time when it caused a train car to derail.

Smith said the S, whether it was burning or just filled in with whitewashed stones, provided a clear sign of school pride for the community.

Assistant Principal Dan Smith said the tradition of setting fire to the letter officially ended in 1988, due to liability issues. But in 2011, a couple students lit it once again as part of a senior project. Today, the S is seen as more a symbol of the city, but Dan Smith said he would welcome restarting the tradition with some type of electric lighting.

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Rattlesnake Ridge’s mark was actually more of an embarrassment for La Salle High School, a Catholic school in Union Gap.

Principal Ted Kanelopoulos said a group of students put an L on the northwest side of Rattlesnake Ridge about 15 years ago. They made the stone marker without the school’s authorization or the permission of the property owners,  Kanelopoulos said.

“When it first went up, La Salle made it clear to the public and the property owners that it was not sanctioned by the school,” said Kanelopoulos, who was a teacher at the time.

As far as he knows, those responsible were never disciplined. And he said the school continues to disavow the marker, as the idea of hillside letters runs counter to the school’s environmental science lessons on being a good steward of the environment.

But the L remained on the hillside, and in recent years some have tried to shape it into a cross, with an outline of the other two arms of the cross on the side of the hill.

Attempts to contact the listed property owners were not successful.

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Some markers remain mysteries, as in the case of the large cross on the Yakima Ridge. State Department of Natural Resources officials say the cross, visible for miles, is on private land, but nearby residents and business people do not know who built it, when it was built or its purpose.

• Donald W. Meyers can be reached at 509-577-7748 or dmeyers@yakimaherald.com. Follow him on Twitter at twitter.com/donaldwmeyers.