0001130464-07-000146 424B7 4 20070427 20070427 BLACK HILLS CORP /SD/ 0001130464 4911 460458824 SD 1231 424B7 33 333-141727 07794550 625 9TH STREET PO BOX 1400 RAPID CITY SD 57709 6057212343 625 9TH STREET PO BOX 1400 RAPID SD 57709 BLACK HILLS HOLDING CORP 20001222 424B7 1 prospectus_supplement.htm PROSPECTUS SUPPLEMENT GRAPHIC 2 img1.jpg GRAPHIC GRAPHIC 3 img2.jpg GRAPHIC GRAPHIC 4 img3.jpg GRAPHIC