In Minnesota, yes it is street legal (each state has different rules).
Here's some fun little "street legal" requirements in Minnesota:
1) 1 mirror
2) Horn
3) Muffler
4) 1, but not more than 2, headlights with hi-lo beam settings
5) Red tailight
6) Pegs for passenger (if equipped with passenger seat/pillion)
7) At least 1 brake, front or rear, operated by either hand or foot
8) Eye protection (windshield does not count, sunglasses do count)
There are a few other little quirky laws here and there based on age and whether you're riding with a permit or license, but those above are the basics.
There are lots of bikes in Minnesota that get "bobbed" and lots of them only have one brake.
Of course, lots of them remove the mirrors, horn and some remove the hi-lo beam settings (i.e. just a standard headlight). I think there are a good deal of bikes on the road that are not technically street legal here. O_o