LeGrande Cannon Boulevard, the 3.12-mile long scenic road that winds along the north flank of Mount Helena, was constructed in 1907-1908 upon the abandoned right of way of the Big Helena Ditch (also known as the Helena Ditch, Big Ditch and Upper Chessman Ditch), an impressive late 19th century hand-dug channel that brought water from Ten Mile Creek to Helena for placer mining operations.

The Boulevard is named for William LeGrande Cannon (1879-1902), the son and heir of Helena mining and real estate entrepreneur Charles Cannon and his wife Catherine. In 1902, William died of tuberculosis in San Diego, California, at age 23. His parents saw the funding of the proposed scenic road as a way to memorialize their son, and donated $5,000 toward its construction.

For an excellent history of LeGrande Cannon Boulevard, with numerous maps and photos, please open the PDF file linked to below. It is a draft version of the National Register of Historic Places registration form for the Boulevard, prepared by Helen L. Rietz and Patty Dean in 2008.