If one thing can be said about County Townships it's they can and do change. They can have boundary changes, name changes, come into existence or cease to exist. The most common reason for changes occur after the US Federal Census Bureau or State Census Commission releases population information based on a recently completed census. However, there are other reasons counties change its townships. Unfortunately the exact dates and reasons for township changes for Marion County were lost in the courthouse fires. Lacking court or county council records we have to rely on information from the US Census Bureau reports and the Census schedules themselves to determine Marion County's Township changes.
    For each US Census the Census Bureau releases Population Statistical Reports. To help find historical information on Marion County's Township changes sub-reports headed Minor Civil Divisions (for Marion County that means by Townships) found within the Statistical Population Reports were used. The information in these reports include such things as: population numbers; notes about the changes in townships between the prior census and the current one; when a new Township came into existence and/or when one went out of existence; what township(s) a new township was created from and whether or not the information on such changes were available for that census period.
    Arkansas became a state 15 Jun 1836. What is now Marion County was created on 03 Nov 1835 out of the western portion of Izard County, Arkansas Territory and was named Marion County. The name was immediately changed from Marion to Searcy. After statehood the First General Assembly of Arkansas received and granted a petition from the county changing the name back to Marion on 29 Sep 1836. On 18 Nov 1837 the boundary line between Marion and Carroll counties was defined (and was defined again 18 Dec 1846). On 13 Dec 1838 Searcy County was formed from Marion County. Marion's West boundary (mostly along Boone County line) was defined 11 Jan 1840 (and again 18 Dec 1846). All of these county and state changes occured between the 1830 and 1840 censuses. Both Searcy and Marion counties had courthouse fires that resulted in the loss of records from these early days.
     The 1840 Census was the first Census taken for Marion Co and it reflected six Townships: Blythe, Buffalo Fork, Little North Fork, Sugar Loaf, Union and White River. (These are noted as "Original Township" in the list below.) Although the 1840 Population Statistical Reports notes that Minor Civil Divisions information is included I've been unable to find a digital copy of any reports online.
    James Cowdrey was the census taker for the 1850 Marion Co census and it is the only Marion Co census that did not produce schedules by townships. Rather beside the householder's name Cowdrey made a one or two character notation designating the resident's Township location. However, we do know that Prairie Township was created between the 1840 and 1850 census because Cowdrey listed it on his schedules. It's apparent some poor statistican was handed this census with instructions to compile the information by townships because the information by township was included in the 1870 Census report.
    On 18 Jan 1855 a part of Fulton County was attached to Marion. The 1860 census Population reports while publishing numerous schedules for all categories of the census it only reported state populations in those categories. Nothing was found on Minor Civil Divisions, however the information for the 1850, 1860 and 1870 censuses is included in the report for the 1870 Census Minor Civil Divisions.
    On 09 Dec 1875 the line between Marion and Boone County was defined. The 1880 Census included information on Minor Civil Divisions, however listed under Marion County it is noted "Information as to changes in minor civil divisions incomplete" for changes between the 1870 and 1880 censuses. (For townships created between the 1870-1880 census the "Created From Township(s) box is empty in the list below.)
    On 09 Mar 1881 the line between Baxter and Marion changed. By the time the 1890 Census was taken Marion County's population had grown - mainly due to the mining boom. After the Census Bureau released its population reports for the 1890 census six new townships were created.
    Between the 1900 and 1920 censuses only a few new townships were created. Between the 1930 and 1940 censuses no Marion Townships have been reported as changed or created.

If you don't understand Townships read an explanation
Sources for US Census Bureau's Statistical Reports by Minor Civil Divisions used to compile the below information.