The Twyn Rivers area was once home to two hotels and one of the last operational mills in the Rouge Valley.

Glen Eagles Vista
This area was once home to the Glen Eagles Hotel. In the 1990s, the site was almost developed into a 10-storey condo building but was saved by quick action from local conservationists.

William Stotts, who was the first resident of this property, built a stone house known as Glen Eagles Manor. In 1931, Henry Massie bought the property and began running horse riding lessons for his two daughters and the public. He served drinks to parents as they waited for their children's lessons to end. The drinks turned out to be more profitable than the lessons and eventually his house, including a dance hall addition, became the Glen Eagles Hotel. It was a popular dining and entertainment destination for locals. The hotel closed in 1989 and burned down shortly after, in 1990.

In 1998, Pauline Browes, a former Member of Parliament and local conservationist, noticed that a 10-storey condo development plan had been approved on the Glen Eagles property. Thanks to the quick action of Browes and other conservationists, including Glen DeBaeremaeker, Jim Robb, Ron Christie, and Don Prince, the site was saved. They raised the $6 million needed to buy the land from the condo developer in just 15 weeks. Today, the Glen Eagles property is permanently protected within Rouge National Urban Park.
Maxwell's Mill
Many sawmills and grist mills were built in the mid-19th century, including Maxwell's Mill, one of the last operational mills in the Rouge Valley. The foundations of Maxwell's Mill can still be found along Twyn Rivers Drive.

Mechanization became increasingly common throughout the 19th century and by 1861, 28 grist mills and 89 sawmills had been built along the Rouge River. Within a few years, however, the Rouge Valley's limited timber supplies were depleted and by 1893 there were only 21 sawmills still operating in the area. One of the last operational mills in the Rouge was Maxwell's Mill.

Maxwell's Mill is a historical site of interest located within the City of Toronto portion of the Rouge. The story begins with James Maxwell, who built the mill in 1840 and began grinding wheat into flour. In 1923, after many decades in business, the Maxwell family decided to sell the mill to Clarence Purcell. Purcell used the property to raise horses and livestock. The mill closed down in 1929 after a flood destroyed the mill dam. Over the following decades, the mill was used first for livestock housing, then as storage space. The mill stood strong, withstanding several floods throughout the years, but in the 1970s it was lost to a fire.

The stone foundations of Maxwell's Mill still exist today and can be seen along Twyn Rivers Drive, close to where the Orchard Trail crosses the road. This interesting heritage site is preserved in Rouge National Urban Park and is part of the City of Toronto's Inventory of Heritage Properties. Evidence of old laneways or "given roads" leading to Maxwell's Mill and other mills in the Rouge Valley can also be seen on some of the trails in the area.
Rouge Valley Inn
The Rouge Valley Inn was once owned by Ambrose Small, a rich theatre magnate who disappeared mysteriously in 1919. The inn was a popular local attraction over the years, but burned down in 1968.

The Rouge Valley Inn was located on the Little Rouge River, near the present-day Twyn Rivers parking lot. Though it started off as a simple home, the Inn eventually became a popular local attraction. It offered dining, entertainment, a dance hall, and a large semi-natural swimming pool, created by damming the river.

Around 1900, the Rouge Valley Inn was bought by Ambrose Small, a businessman who owned several theatres across Ontario. In 1903, he married Teresa Kormann and used her sizeable inheritance to acquire the Grand Opera House on Adelaide Street in Toronto, one of his long time business ambitions. Small built up a chain of 34 theatres and became a millionaire. However, he also had a reputation as a heavy gambler and a ladies’ man.

On December 1, 1919, Small sold his theatre chain to a company called Trans-Canada Theatres Ltd. for $1.7 million. The next day, he met with his lawyer at his office in the Grand Opera House. Later that night he went missing. His lawyer left the office at 5:30 pm and was the last person to see Small alive. The police conducted a massive manhunt and launched an investigation into his disappearance, but the mystery was never solved. The case was eventually closed in 1960.

Meanwhile, the Rouge Valley Inn continued to operate and became known as the Rouge Valley Olympic Inn. Across from the Inn was the Caper Valley Ski Hill, which had tow ropes, a T-bar, a restaurant, and a clubhouse. The ski hill is no longer operating, but the grassy slope at the north end of the Mast Trail, near the Twyn Rivers parking lot, is where the former ski hill site once stood. Today, the Rouge Valley Olympic Inn no longer exists, as it caught fire and was destroyed on October 23, 1968. Arson or faulty wiring were suspected to be the cause of the fire.