Is there any special reason that African-Americans chose to take
surnames ending n "ton"?

Dear Idoruby, 

The most common names among African Americans do not end with "- ton",
but rather with "son" :

1. Johnson
2. Brown
3. Smith
4. Jones
5. Williams
6. Jackson
7. Davis
8. Harris 
9. Robinson
10. Thomas 

(SOURCE: Boston Family History,
<http://www.bostonfamilyhistory.com/name_africa.html>).

In general, "Many slaves didn't receive a last name until they were
freed. Sometimes a slave took (or kept) the last name of their former
master, or took a common name from the area in which they lived. Some
African Americans adopted the names of famous Americans such as
Washington, Jefferson, Jackson, or Clay, or from those who helped
African Americans at the time, such as the 19th century abolitionist
John Brown. According to Stuart Berg Flexner in his book Listening to
America, many African Americans took the last name of Howard in honor
of General Oliver Otis Howard, who was a Union general in the Civil
War and head of the Freedman's Bureau from 1865-1874, and also the
founder and early president of Howard University. The name Howard
became so popular a name with African Americans at the time, that in
the 1980s about one-third of all Howards in the United States were
African American." (SOURCE: ibid).

So, the reasons for the naming with the suffix -ton are various: Names
that end up with "- ton" could be, hence, names of places (a common
Anglo-Saxon suffix, meaning "town, enclosure" in Old English), it
could be a name of a person who inspired the family, and it could be
the name of the slave-owner, as sad as it sounds.

For comparison, here are the 10 most common names in general, among
all ethnic groups in the United States:
Smith (1.006%) 
Johnson (0.810%) 
Williams (0.699%) 
Jones (0.621%) 
Brown (0.621%) 
Davis (0.480%) 
Miller (0.424%) 
Wilson (0.339%) 
Moore (0.312%) 
Taylor (0.311%) 

See also: 
African American Names and Naming: The Social Real and Fiction
<http://www.cl.uh.edu/itc/course/LITR/5731/rp1ad.htm> 

I hope this answered your question. Please contact me if you need any
clarification on this answer before you rate it.

Thanks.