MONTICELLO — Discovered in the back of a closet behind some built-in shelves of the Robert Allerton mansion was some of the home’s original wallpaper.

Anne Carlson, who is assisting Allerton Park staff and other volunteer committee members on restoration of the mansion’s interior, knew a company in England was still producing it more than 100 years later.

Carlson’s knowledge has proven invaluable as the effort proceeds to restore the elegant mansion, built in 1900, to its former glory.

“Robert took the European tour,” she said. “He based the house design on a famous English house, the Ham House” — a 17th Century mansion on the banks of the River Thames near Richmond.

Keeping the architecture and feel of the house has been hit and miss over the years. So when Carlson was asked to serve on the Allerton building and grounds committee, she agreed.

“Things have been hodge podge out there,” she said. “If one of the bed linens had gotten damaged,” staff would improvise with what was readily available.

One of the things she did was to suggest a plan. A review of how things are purchased “was helpful to start to create a consistency in the rooms so guests who come out there have a clear idea of what kind of room and experience they’ll get and what amenities they’ll have.”

The three-story mansion is open to guests.

Retreat Center Manager Jordan Zech said planning and fundraising for the updates have been in the works for a couple of years.

“But the lack of mansion guests during the pandemic really created a great opportunity to get started,” he said.

The upgrades are being made thanks to donor support that has hit half a million dollars for three rooms of the mansion. A total of $5.5 million toward an $8 million goal has been raised for the ALL In for Allerton/With Illinois campaign goal, which is for the entire park, not just the mansion.

Zech noted that when Robert Allerton donated his 1,500-acre estate to the University of Illinois in 1946, most of the furnishings in the Georgian-styled house were given away.

Carlson said a mix of antiques, reproductions and new pieces are being used to furnish the spaces.

“With a house that’s over 100 years old, there are surprises,” Carlson said.

One of those was finding many of the original rugs in the attic, where they had been stored for 60-plus years. The rugs had been cleaned and wrapped.

“They’re just unbelievable!” Carlson said. “Some are over 40 feet long. I believe these rugs were meant to be used.

“This is a living, breathing building, and people will really enjoy seeing them and using those pieces. They’re incredibly gorgeous. Some of them do need to be repaired.”

Also in the attic, Carlson found artwork and a few pieces of furniture, some of which she hopes to have restored.

Work on Allerton’s room is finished. Guest rooms on the third floor, which have European (shared) bathrooms, have been completed. There are 14 guest rooms that housed Allerton’s staff.

The other four second-floor rooms are Robert’s room; one for his adopted son, John Gregg; one for Allerton’s stepmother, Agnes; and the family room, which was originally two rooms that he combined. (There are a total of 42 guest rooms on the property.)

The Butternut Room was originally a dining room, and Allerton renovated it shortly after moving in to become a small library. This room was endowed and has undergone a renovation, which is almost complete except for the placement of a sculpture that Carlson hopes to obtain from the Krannert Art Museum’s collection.

“It’s a really cozy sitting room with a window seat designed by John Gregg in the ’30s,” said Bridget Frerichs, the center’s associate director of advancement.

The main floor also includes the library, which Allerton renovated from the original music room to house his expanding collection of books; the solarium, which was a garden room and overlooks the property; the Pine Room, which houses some of the original furniture and art, along with the Oak Room, which was Allerton’s office and houses some original art.

There is also the Grand Gallery, which is used for weddings and events, the marble hallway, which Allerton added to connect the house to what used to be the stable and later became the carriage house.

The basement was built after the University of Illinois acquired the property and is a games room currently.

“Blending reverence to the history and architecture of the mansion, while using durable materials that suit the commercial use of the spaces, is of great importance to provide a renovation that will withstand the test of time,” said Carlson, who is owner-operator of Champaign’s Ann Carlson Designs and is undertaking the Allerton work on a volunteer basis.

She estimates she spends the equivalent of one week a month on the house.

A transplant to the area, Carlson had no idea the estate existed and was “blown away” when she saw the house.

Historical photos and information about Robert Allerton’s travels have been used to inspire the overall design. Allerton not only traveled to Europe but spent much time in Asia, according to Frerichs.

“He would collect artwork as he traveled, sometimes commissioning an artist to make a replica or original piece for him,” she said. “He had a somewhat eclectic and artistic compilation of items, which has been fun inspiration to draw from.”

Carlson has researched that period “to determine what would have been popular in that time — the fabrics, furnishings and finishes.