SANTA ROSA PLATEAU - The first was built in 1846, a time when the opening salvos of the Mexican War were sounded. The second went up a decade later when the nation's moral seams were being stretched taut leading up to the Civil War.

Today, the Moreno and Machado Adobes, believed to be the oldest standing structures in Riverside County, are popular hiking destinations for visitors to the 8,000-acre Santa Rosa Plateau Ecological Reserve.

As Southwest County has evolved from a western wilderness to one of the country's fastest-growing areas and cattle drives have given way to herds of road-weary commuters, the two adobes that served as shelters for bone-weary ranch hands for more than a century have stood side by side on the plateau west of Murrieta.

However, there is concern these two landmarks may slowly be crumbling from the inside out.

While no one involved in their care is pushing the panic button, the keepers of the landmarks are hoping to get a glimpse at the building's adobe brick walls, which were sealed with cement a half-century ago, to see if time and moisture are causing them to deteriorate.

It's a brick house

Among the oldest building materials on earth, adobe bricks are made with a mixture of water, clay, straw and sometimes manure that is poured into a mold to harden and then removed and allowed to dry in the hot sun.

The bricks take up to 30 days to harden and as many as 5,000 of them are needed for a small adobe building.

Water is the great enemy of adobe, which can crumble over time if exposed to moisture.

In the 1800s, adobe walls were generally sealed with a mixture of lime, horsehair and animal blood. The mixture kept water away and also allowed air to reach the bricks.

However, sometime during the Vail family's ranching days on the Santa Rosa Rancho - the family grazed cattle on the plateau from 1904-64 - the original sealant on the adobe's walls was replaced by cement.

While the intent might have been good - would you want walls covered with horsehair and cow's blood? - or at least economical, the air-tight cement is not good for adobe bricks.

"The cement seals in moisture," said Rob Hicks, an interpreter on the plateau for the Riverside County Regional Park and Open Space District. "And it doesn't allow the adobe bricks to breathe."

Life on the plateau

In 1846, California Gov. Pio Pico granted the 48,000-acre Santa Rosa Rancho to Juan Moreno, who built a four-room adobe house there for his family.

Moreno grazed cattle and raised vegetables during his ownership of the land.

The Moreno adobe was reduced to just one room by fierce rain storms in 1884, according to author Steve Leech, author of the 2004 book "Along the Old Roads - A History of the Portion of Southern California that became Riverside County."

"The building still stands today on the Santa Rosa Rancho and is one of the oldest, if not the oldest, remaining buildings in Riverside County," Leech wrote.

In 1855, Moreno sold the Santa Rosa Rancho to Augustin Machado for $1,000 cash and $500 in livestock. Machado never lived on the rancho, but instead built himself a large home on another property he owned, Rancho La Laguna, known today as Lake Elsinore.

Machado also grazed cattle on the land and built a larger adobe next to the Moreno adobe for his vaqueros.

"These two buildings together give a good indication of what life was like during that period of California history," Leech wrote.

Machado died in 1865 and his property was divided among family members. In 1876, the Santa Rosa Rancho was sold to a group of English and American investors, one of them an Englishman named John Dear. When John Dear died in 1884, his son, Parker, bought the Santa Rosa, including the adobes, from his father's estate.

In 1881, Parker Dear married Elena Couts, the daughter of Cave and Ysidora Bandini Couts of Rancho Guajome near Vista. That beautiful rancho served as the social center for a large part of San Diego County.

Dear built a 14-room Victorian-style home with eight bedrooms and two dining rooms on the Santa Rosa. The nearby adobes served as a bunkhouse and blacksmith shop for his cattle ranch.

Dear became a successful cattle rancher and endeared himself to the growing community of Murrieta by holding an annual May Day picnic that attracted hundreds of guests each year.

When a Southern California land boom in the early 1880s went bust at the end of the decade, Dear, who had sought to develop part of the rancho, suffered financial woes and mortgaged his property to the San Francisco Savings Bank. The bank foreclosed on the property in 1893 - the year Riverside County was established - and the rancho passed through several hands until it was sold to Walter Vail in 1905.

The Vail family - which bought about 85,000 acres of land in Southwest County - brought part of their cattle ranching empire to the Santa Rosa Rancho, using the lush, grassy expanse for grazing.

The family, whose local ranch was headquartered in Temecula, had other financial interests that stretched from their Empire Ranch in Tucson, Ariz., to Santa Rosa Island off the Southern California coast.

However, on holidays and other special occasions, the family would often gather to celebrate at the Victorian home built by Dear.

The Vails continued to use the Machado adobe as a bunkhouse for their cowboys, while the smaller Moreno adobe served several purposes - including, some say, a holding cell for drunk cowboys, dubbed "Vail's Jail." The metal bars that remain on one of that adobe's windows lend credence to the tale.

The Vails sold their local land holdings in 1964 to the developers of the planned community of Rancho California.

A decade later, Parker Dear's lavish home burned to the ground.

Saving the land

In the mid-1980s, with developers eyeing the plateau west of Murrieta for houses, the Nature Conservancy bought 3,100 acres of land there to safeguard it from urban sprawl.

In the years since and in partnership with several government agencies, including Riverside County and the Metropolitan Water District, land was added, expanding what has become the Santa Rosa Ecological Reserve to 8,300 acres.

Within the reserve's boundaries, dozens of rare or endangered animals and plants can be found along with vernal pools, flowing creeks, stately oaks and large expanses of native grasses.

And the adobes.

In 2006, most of the reserve came under the jurisdiction of the state when the California Department of Fish and Game bought the land from the Nature Conservancy.

Carole Bell, who 14 years ago took a job as a caretaker for the Nature Conservancy on the plateau and went on to become the manager of the reserve for the conservancy, now manages the plateau for the state agency.

Bell, who lives on the reserve a short distance from the adobes, shares the concern about the integrity of the buildings.

"The adobe bricks can dry out and lose their structure," Bell said. "It would be good to investigate."

That was Bell's intention about seven years ago when several fundraisers were held to raise money to renovate the adobes.

Sufficient money was raised to put a new roof on the larger Machado adobe, but not enough to do the other work.

The consultants who did the work on the roof recommended to Bell opening a section of the cement covering the walls for an evaluation of the adobe.

That has yet to happen.

"If you get up in the attic, you can see some of the exposed adobes that weren't covered with cement," Bell said. "And they seem to be holding up OK."

Still, both Bell and Hicks hope to find a way to check out the bricks they can't see.

"We're going to have to get some experts in here to do that," Bell said.

Saving history

Bruce Coons is an adobe expert and the executive director of San Diego-based Save Our Heritage Organisation, a nonprofit group dedicated to promoting and supporting the preservation of architectural, cultural and historical links and landmarks.

"I've been interested in adobe restoration since I was a child," Coons said.

Formed in 1969, in addition to helping preserve some of San Diego County's oldest buildings, among its other activities and projects, SOHO holds workshops - dubbed "Adobe U" - to train volunteers to repair and maintain old adobes.

"It's actually pretty simple technology," Coons said. "Everything can be dealt with."

He should know. Coons and his wife live in Pomona in an adobe house built in 1837.

He agreed cement is not a good sealant for adobe bricks.

"(Cement) actually attracts moisture and can trap it inside," he said. "Once the moisture gets in, it isn't allowed to dry."

Among SOHO's more recent projects in San Diego County was the restoration of the St. Francis Chapel at Warner Springs. The group is also involved in work at Rancho Guajome near Vista, which is owned by San Diego County and was the childhood home of the aforementioned Elena Couts.

Coons said he has yet to visit the Moreno or Machado adobes, but has seen many pictures of the buildings.

Though the local adobes are slightly outside the area in which his group normally works, Coons said he is willing to consult on any restoration work.

"I'd be happy to help out in any way we can," he said.

An old cowboy

The two adobes are not generally open to the public, although on summer weekends a docent from the reserve's visitor center is often available to unlock the doors for visitors.

Those who do go inside find pictures of the Vail and the Dear families on the walls and several glass cases filled with artifacts from the bygone era.

One day about eight years ago, an older gentleman came up to Bell and asked if he might be able to go inside the adobes.

"My name is Guy Flint," he told Bell. "I used to be a cowboy for Mahlon Vail."

Bell was happy to open the adobe for the old cowhand who more than 60 years ago slept in the bunkhouse and worked the ranch.

Since then, the two have corresponded and Flint, now 90 and in an assisted-living facility, has described to Bell what life was like living in the adobe.

"The middle room in the larger adobe was used as a bunkhouse for the ranch hands," Flint wrote to Bell. "The room had four army-type cots, a few old chairs and a stove. Three or four of us slept in the bunkhouse and the cook slept at (Parker Dear's house)."

Three cement steps that led to the front door are about all that remain of the Dears' Victorian home, located a short walk from the two adobes

"And the roses," Bell said. "Don't forget the roses. Mrs. Dear brought them with her when they moved here in the 1880s. They bloom every year."

- Contact staff writer John Hunneman at (951) 676-4315, Ext. 2603, or hunneman@californian.com.