It is thought that during the Anglian stage of glaciation, ice pushing south from the main Wensleydale stem, created the bowl shaped nature of the upper valley.

[4] It was first recorded in 1280 as Snaysum or Snaysome, when the vaccary (a name for the cattle farms in upland regions of the Pennines) was listed as £6 per year (equivalent to £7,000 in 2023).

[5][6] In the seventeenth century, a survey listed the valley as being either Snaisholme or Snailsholme, which was in the township of Hawes with a population of nine, eight house, 30 outhouses and 268 acres (108 ha) of meadow lands.

[15][11] In 2021, the woodland trust proposed a scheme which would involve planting birch, rowan, oak, willow and Scots Pine trees across 550 acres (220 ha) of land within Snaizeholme valley.

[21] The land is mostly carboniferous limestone, with shales and coal measures deeper down, and an isolated pocket of millstone grit to the south-east of the dale where it rises up to the peaks.

[33] An extreme rainfall event in May 1959 sent floods down the valley into the River Ure, which trapped a man up to his waist in floodwater and washed away sheep and lambs.

[49] The conservation and reserve status has been so successful, that red squirrels have been spotted in gardens in Hawes, the nearest town, and Bainbridge further down the valley.

[50] The creation of new woodland, including deciduous trees, has also benefitted other wildlife, with bird species increased from thirty types to seventy, and water voles and pine martens spotted in the valley.