Blue mills landing aka Twyman MO see notes below about the Tuymans of Jackson Co, was platted around a mill on the Blue River. A post office was in place from 1835 to 1895.
Twyman
Description: A town in northwestern Fort Osage Township. The name was changed from Blue Mills to honor a pioneer doctor, Dr. L.W. Twyman. The town Blue Mills was located one-half mile east from the mill for which it was named, Blue Mill (q.v.). The government postal guides gives the post office name Blue Mill from 1870-1891, and Bluemill from 1892-1896. Twyman is first listed as a post office in 1899. At least as early as 1843, Blue Mills was the principal landing on the Missouri River for river trade for Independence. At a still earlier date the place was known as Hedspeth Settlement for William Hudspeth, one of the prominent pioneer settlers. (Postal Guide 1870-1891; 1892-1896; 1899-1902; HIST. JACKSON 1881, 104, 105; H.P. Chiles)
Source: Atchison, Anne. "Place Names Of Five West Central Counties Of Missouri." M.A. thesis., University of Missouri-Columbia, 1937.
This indicates the locale is actually in Jackson County, on the south side of the river not Clay county.
Place name: Blue Mill
Description: An early day mill near the mouth of the Little Blue River. (Woodson 1920; Withers; H.P. Chiles)
Source: Atchison, Anne. "Place Names Of Five West Central Counties Of Missouri." M.A. thesis., University of Missouri-Columbia, 1937.
Place name: Blue Mills
Description: See Twyman.
Source: Atchison, Anne. "Place Names Of Five West Central Counties Of Missouri." M.A. thesis., University of Missouri-Columbia, 1937.
Place name: Blue Mills Ferry
Description: A ferry across the Missouri River which landed on the Jackson side near the Blue Mills (q.v.). (H.P. Chiles)
Source: Atchison, Anne. "Place Names Of Five West Central Counties Of Missouri." M.A. thesis., University of Missouri-Columbia, 1937.
This 1877 Atlas of Jackson Co shows the Hudspeth property holdings near the mouth of the Little Blue in Osage township. Its just a bit northwest of Sibley. The area was known for its southern leanings during the war.
http://www.historicmapworks.com/Map/US/1259580/Blue+and+Fort+Osage+Townships++Atherton++Sibley/Jackson+County+1935c/Missouri/
John R