It is one of the most popular tourist destinations in the area with over half a million visitors per year in the 1970s and is managed by the National Trust.

Tarn Hows is fed at its northern end by a series of valley and basin mires and is drained by Tom Gill which cascades down over several small waterfalls to Glen Mary bridge: named by John Ruskin who felt that Tom Gill required a more picturesque name and so gave the area the title 'Glen Mary'.

The remaining enclosed land and many of the local farms and quarries were owned by the Marshall family of Monk Coniston Hall (known as Waterhead House at the time).

In 1913 G.D. Abraham said "Tarn Hows is set wildly among larches and heather slopes, more like a highland lake than the other waters in Lakeland... more suitable for pedestrians than motorists".

Beatrix Potter's husband, William Heelis of Sawrey, was solicitor for the Marshall family and so was aware of the possibility early on.

[3] Neither the National Trust nor the Forestry Commission could obtain the whole sum quickly enough and Potter's mother would not lend her the money.

The National Trust have made a number of more recent changes to the area including moving the car parks to a less obtrusive place in the 1960s and general footpath and road improvements to minimize the damage caused by the visitors.

In May 2008 a building designed to harmonise with the landscape was opened, providing toilets and an information display under a sedum green roof.

Trees in this woodland support lichen species including Lobaria pulmonaria, Thelotrema lepadinum and Lecidea cinnabarina.