Hello.I am another descendant from the Illinois/Oregon line of Fallins and thought I should weigh in. So far I have been able to trace my family history back to Dorchester/Somerset Counties on the eastern shore of MD.
My ancestor David Fallen was born in MD ca. 1771.I have not yet located his parents.David Fallen settled along Locust Creek in Bracken County, KY in 1808.He had at least three sons:John, William and Henry (my ancestor).(He had several daughters too, but their married names are not known and I haven't been able to trace them further.)David Fallen died in 1849 in Bracken Co.
Sons William and Henry Fallen are in the 1850 census for Bracken Co.John is gone, and I believe may have moved across the River to Ohio - probably Clermont County.
By 1860, Henry Fallen/Fallin has relocated to Vandalia, Fayette Co., IL..Some of his now-grown sons have settled in other parts of IL, in particular Mattoon, Coles Co.Several of his sons served in Illinois Regiments during the Civil War.After the Civil War subsequent generations began moving to the western states, especially CA and OR.
The Oregon Fallins mainly descend from Henry's son Benjamin Franklin Fallin who settled in Douglas County Oregon sometime between 1870 and 1880.Hopes this helps.