The following article contains an answer for the question: After the name of forest reserves were changed, what were two national forests were combined into? , can you please find it? 

Boise National Forest was created on July 1, 1908, from part of Sawtooth National Forest, and originally covered 1,147,360 acres (4,643.2 km2). By the Forest Reserve Act of 1891, the U.S. Congress granted the U.S. President the authority to establish forest reserves out of Public Domain Lands that were subject to disposal (homesteads, sales, etc.) administered by the General Land Office, which had been placed under the authority of the U.S. Department of the Interior in 1849. With the passage of the Transfer Act of 1905, forest reserves were transferred to the U.S. Department of Agriculture in the newly created U.S. Forest Service. Present-day Boise National Forest was first protected as part of two forest reserves by proclamations issued by President Theodore Roosevelt: Sawtooth Forest Reserve (created on May 29, 1905, and expanded on November 6, 1906) and Payette Forest Reserve (created on June 3, 1905). After forest reserves were renamed national forests in 1908, Boise National Forest was split from Sawtooth National Forest into an independent national forest. On April 1, 1944, the entirety of what was then Payette National Forest was transferred to Boise National Forest, and simultaneously Weiser and Idaho national forests were combined to reestablish the present-day Payette National Forest, which is to the north of Boise National Forest. In 1933 the Boise Basin Experimental Forest was created on 8,740 acres (35.4 km2) of the forest near Idaho City to study the management of ponderosa pine. The Lucky Peak Nursery was established in 1959 to produce trees for planting on burned or logged lands on the national forests of the Intermountain region.After the creation of the Civilian Conservation Corps (CCC) in 1933, nine camps and eight subcamps were set up in Boise National Forest, but the number of camps was reduced from 1934 until the program was closed in 1942. Work conducted by the CCC included fire suppression, fish habitat improvement, and construction of guard houses, fire lookouts, campgrounds, roads,...

Payette National Forest