One of Riverside’s architectural treasures is on the market, completely restored and yours for a cool $1.6 million.

The Frank Lloyd Wright-designed former coach house at 336 Coonley Road was part of the original sprawling Avery Coonley Estate, built between 1907-11 and considered one of the crowning achievements of Wright’s Prairie-style years.

Dean and Ella Mae Eastman, who owns three-quarters of the estate, including the main living quarters, purchased the coach house in September 2005, and spent two years completing an adaptive renovation of the building and its grounds.

The coach house, along with the rest of the Coonley Estate buildings, was designated a National Historic Landmark in 1970.

The exterior has been restored to recreate its original appearance as much as possible. Inside, the building has been transformed into a three-bedroom, 4.5-bathroom home. The walled, sunken garden outside was restored using Jens Jensen’s 1913 Coonley Estate plan.

Dean Eastman personally restored over 80 original art glass windows and the building was given a complete structural overhaul including new mechanical systems-air conditioning, radiant heating, sewer and electrical.

Eastman, who was also responsible for restoring the main section of the Coonley residence, served as restoration architect and project manager for the coach house’s renovation.

“It’s wonderful,” said Charles Pipal, chairman of Riverside’s Preservation Commission. “The amount of effort [Dean Eastman] put into it, with really meticulous attention to detail, most people don’t do that.”

It was Eastman who in September 2005 rode to the rescue of the Coonley Coach House, which had fallen into disrepair, suffering from a leaky roof that had compromised some structural aspects of the building.

At the time, the home was owned by Carolyn Howlett, an artist and art educator who saved the home from demolition in the 1950s. The Cook County Office of the Public Guardian was responsible for managing the estate of Howlett, who suffered from Alzheimer’s disease.

The public guardian sought to replace the original red clay tile roof with asphalt shingles, a plan that was rejected by the Riverside Preservation Commission, whose delaying action set the stage for Eastman to buy the home, with the provision that Howlett could remain in the home.

Howlett died on Dec. 17, 2005 at the age of 91. According to records obtained from the Cook County Recorder of Deeds, the Eastmans bought the coach house for $350,000.

In the spring of 2006, Eastman began the massive restoration campaign. In January 2008, the Eastmans received the Frederick Law Olmsted Society’s 2007 Architectural Restoration Award in recognition of the effort.

At one time, Eastman considered reuniting the coach house and the main part of the Coonley Estate, but eventually decided against it.

“We don’t warrant that much house,” said Eastman on Monday. “With 12,000 square feet of house and gardens, it becomes quite a burden.”

The house is being marketed by Marcee Gavula of Baird & Warner Real Estate of Oak Park/River Forest. Gavula is familiar with selling Frank Lloyd Wright masterpieces, having sold the 1902 Heurtley House in Oak Park in January 2007 for $2.5 million.