The Whiskey Ginger is the most forgiving drink on the back bar. Irish whiskey is the classic (in a lot of pubs, "Jameson and ginger" is one word), but bourbon, rye, Canadian, and blended Scotch all work. Ginger ale's sweetness and mild bite cover rough edges, and a squeeze of lime keeps it from tipping into soda-fountain territory.
Ginger ale forgives a cheap whiskey. It doesn't forgive warm ginger ale.
History
There is no inventor and no date. Whiskey and ginger ale is what happens when a bar has both on hand, and dry ginger ale has been a standard mixer since Canada Dry's "Pale Dry" style took hold in the early 1900s. The Irish whiskey version became a pub fixture on both sides of the Atlantic as Jameson grew into the world's best-selling Irish whiskey.
Two near relatives are worth knowing. Add real lime juice and the old bar books call it a Buck. Cut the ginger ale with soda water and you have a Presbyterian, the drier, older-school version.
The Spec
Two ounces of whiskey, four ounces of ginger ale, a glass full of ice, a lime wedge squeezed in. 1:2, same as the Rum & Coke and for the same reason. Sweet mixers need the higher whiskey share to keep the drink from tasting like soda.
Ginger Ale, Not Ginger Beer
Ginger ale is lighter, sweeter, and gentler than ginger beer. Canada Dry, Schweppes, or Fever-Tree's ginger ale are all fine. Swap in ginger beer and you're making a Kentucky Mule without the lime juice, which is a good drink but a different one.
Which Whiskey
Irish whiskey is the default: Jameson, Powers, Tullamore D.E.W. Their light, smooth profile sits under the ginger without fighting it. Rye gives you more spice and makes a sharper drink. A wheated bourbon goes softer and rounder.
Bottom Line
Cold ginger ale, a measured pour, a squeezed lime. Order it anywhere. It'll be fine.