Historically, many streets in Boise were constructed with a "tree lawn" or parking strip built into the public right of way and situated between the public sidewalk and the public street. In the 1970's, Boise City surrendered management of public streets to a county-wide "highway district", the Ada County Highway District (ACHD).
At about the same time ACHD took over management of public streets in Boise, the design of streets in Boise changed as well. Parking strips were mostly eliminated while the streets were widened and sidewalks placed adjacent to street curbs. There was no longer any room for public street trees as Boise expanded. This had the effect of discontinuing the expansion of the public portion of Boise's urban forest, except where new parks were constructed.
Since the 1970's Boise's street tree population has remained largely stagnant. There are few new tree lawns or public rights of way on which to plant street trees. Therefore, the benefits the street trees provide are not regularly available to areas developed since that time. In rare cases where new tree lawns were constructed, they were often too narrow for tree planting or growth. Much of West and South Boise has been developed with the "new" street standards. Therefore there are very few public street trees in these areas, and the benefits of a street tree canopy are limited.