The Lewis & Clark Conservation District was organized in June 1948. It originally included all of Lewis and Clark County except a portion in the northeast corner, which was part of Cascade County Conservation District, and it included part of Jefferson County lying north of the Boulder Hill. It excluded the 1948 city boundaries of Helena and East Helena.
In 1961, the portion of Lewis and Clark County in Cascade County Conservation District was made part of LCCD. In June 1966, the part of the District in Jefferson County was made a part of the Jefferson Valley Conservation District.
Areas of Helena and East Helena that were annexed since 1948 are included in the Conservation District.
There are 1,288,258 acres in Lewis & Clark County, not including National Forest land. That amounts to 2013 square miles. There are 54 miles of the Sun River paralleling the county line with Teton Conservation District. 696,960 of over 1.4 million acres of the Sun River Watershed are located in Lewis & Clark Conservation District.
Membership of the first Board of Supervisors consisted of Myrlin Donaldson, George Diehl, Gilman Mirehouse, Robert Mosher and Adolph Burgraff. Brick Vaughn served as the first District Secretary and Rex Campbell and Homer Turner were the first technicians with the Soil Conservation Service.