On this day in History - April 7

451 – Attila the Hun captures Metz in France, killing most of its inhabitants and burning the town.

1141 – Empress Matilda becomes the first female ruler of England, adopting the title "Lady of the English".

1868 – Thomas D'Arcy McGee, one of the Canadian Fathers of Confederation, is assassinated by a Fenian activist.

1948 – The World Health Organization is established by the United Nations.

2001 – NASA launches the 2001 Mars Odyssey orbiter.