On the menu, with each dish priced.
This is of French origin - according to the card (the 'card' is the menu card). This applies to meals which are ordered in separate items, each with a specified price. As distinct from a table d'hôte, which has a fixed inclusive price.
The date of the earliest French usage isn't known. In English the first citation is Joseph Sherer's, Notes and Reflections During a Ramble in Germany, 1826:
"He will find comfortable apartments, civil attendance, excellent fare, à la carte, at any hour."
See also - other French phrases in English.