Because race is sociological there is no such thing as half of anything being considered white. Half-asian americans are considered asian and half latinos are considered to be be latinos. If you didn't know Obama's history you would consider him to be pure black not bi-racial.
Anyway let us relish in the significance of this event.
This is a Norman Rockwell painting of Ruby Bridges ...
... the little black girl who had to be escorted to school by federal marshals. "On November 14, 1960, nearly 48 years ago, Bridges faced hostile crowds as the first black child to attend a previously all-white New Orleans school. She was 6 years old and had only been told by her mother that she was going to be attending a new school that day and 'had better behave.' Little did she know that she would be bombarded with jeers and even death threats, and that she would end up being the sole child in her first grade class after other children were kept home by their parents." All because Ruby was Black.
48 years later -- January 5, 2009 -- here is a picture of Sasha Obama, a little 7 year old Black girl, being escorted to school by her mother, First Lady-elect Michelle Obama, and the Secret Service because Sasha's daddy is now President-elect of the United States, Barack Obama.