There is an article translated from Japanese on the history of Shimpaku at the World Bonsai Friendship Federation website.

JUNIPERS

Juniperus procumbens  $409	Juniperus chinensis 'Shimpaku'  $324	Reverse of 'Shimpaku'
PROCUMBENS This variety of juniper is native to southern Japan and the western coasts of Korea and is closely related to Juniperus chinensis and is sometimes treated as a variety of it as J. chinensis var. procumbens.	'SHIMPAKU' is a variety of Juniperus chinensis 'sargentii,' the Japanese botanical name is Miyama-Byakushin, belongs to the Cupressaceae family.
Procumbens Naturally prostrate, the needles (leaves) are arranged oppositely in whorls of three with successive leaf pairs perpendicular. All the leaves are junenile form, needle-like 6-8 mm long (1/4-1/3 inch) with 2 white stomatal bands.	Shimpaku has scale-like gray-green to dull dark green needles soft to the touch.
Juniperus occidentalis var. occidentalis
WESTERN JUNIPER range is in the extreme northeast corner of California, also in Oregon, Washington, Idaho and Nevada. Not to be confused with Juniperus californica or Juniperus o. var. australis/SIERRA JUNIPER which grow farther south in coastal and desert mountains. This mature specimen was photographed near Pluto Caves in Siskiyou County and is 25-30-feet tall.
J. occidentalis bark is furrowed and shreddy and whip leaves are dark green. Similar to the procumbens, they are arranged in opposite decussate pairs or whorls of three. Adult leaves are scale-like 1-2mm (.03-.07 inches)long and the junveile leaves are needle-like 5-10mm long (.19-.39 inches).