State Route 51 (SR 51) begins at SR 99 and heads north toward Interstate 80. At an interchange southeast of downtown Sacramento, Business 80 turns north onto unsigned SR 51 near its southern end. US 50 continues east, SR 99 heads south, and the unsigned I-305 ends. The elevated freeway carrying Business 80 east of downtown is between 29th and 30th Streets, and an older section beginning at A Street and continuing northeast was originally known as the Elvas Freeway (and originally signed as US 99 east). On this section of freeway, Business 80 crosses the American River before its northeast-bound merge with the North Sacramento Freeway (the northern portion of SR 160 towards downtown).