[1][2][3] The Musashino Kannon Pilgrimage was founded by Jōe Shibata, who was a Japanese local historian, in 1940, and the opening event was held at Sanpō-ji, which is third one in the temples list, on May 1, 1941.
It is because the area suffered war damage, so the temples could not ready to accept pilgrims.
Thereafter the Musashino Kannon Pilgrimage Ground Association was reorganized on April 2, 1993, and the official website has also opened.
In 2000, all the temples did kaichō, which is public exhibition of religious objects, to commemorate the 60th anniversary of the founding.
For this reason, traveling for pilgrimage becomes gradually difficult, but it's hiking level, not climbing.