"Nation" chronicles this journey, giving it, as only photographs can, a gripping human face. Make that many faces. Some are well-known, like the mustached Albert Einstein wearing an Indian headdress. But most are your everyday Americans, from the sober Dutch women in their white winged hats at Ellis Island in 1910 to the Japanese-American children in their paper samurai headdresses at a 1987 Japanese street festival in Chicago.