Short answers, pulled from the story.
Napoleon Bonaparte issued a direct order to General Jean Victor Marie Moreau on the 1st of March 1800 to divide his command into four distinct corps. This date marks the formal introduction of the corps as a legal military formation.
A typical corps contained cavalry, artillery, and infantry within one independent unit. The French Imperial Army used these formations as the first combined-arms groups with stable manning.
The Australian and New Zealand Army Corps fought at Gallipoli in 1915. Two corps were raised in early 1916: I ANZAC Corps and II ANZAC Corps.
The Canadian Corps consisted of four Canadian divisions from inception until the war ended. It maintained this composition unlike British corps which changed frequently in France and Flanders.
Congress legalized the first field corps in the United States Army on the 17th of July 1862. President Lincoln ordered their creation in March 1862 instead due to delays by Major General George B. McClellan.