Since Margaret was married at age 17, based on the 1930 census data, one might expect that she lived in Massachusetts at the time.
Christina Campbell (age 9), with siblings John, Daniel, Peter, Pearl, Ruth and Jeanette, lived with parents, John W. and Jennie Campbell in Boston, Massachusetts in 1920. The census said that they had immigrated from Prince Edward Island in 1910. 
1940: living on Baldwin Street in Boston, Suffolk Co., Massachusetts. Age 29. Lived in same place in 1935.
"United States Census, 1920," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MFMZ-781 : accessed 3 October 2020), Christina Campbell in household of John W Campbell, Boston Ward 3, Suffolk, Massachusetts, United States; citing ED 65, sheet 4B, line 86, family 85, NARA microfilm publication T625 (Washington D.C.: National Archives and Records Administration, 1992), roll 729; FHL microfilm 1,820,729.
"United States Census, 1930," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/XQ5P-KK3 : accessed 27 May 2014), Margaret Davidson in household of Robert Davidson, Boston (Districts 1-250), Suffolk, Massachusetts, United States; citing enumeration district (ED) 0059, sheet 2A, family 34, NARA microfilm publication T626, roll 943.
Thank you to Dillon Gray for creating WikiTree profile Campbell-7677 through the import of Gray Family Tree (2).ged on Aug 19, 2013. Click to the Changes page for the details of edits by Dillon and others.
Campbell-14759 was created by O Westgarth through the import of ged 15.GED on Jul 6, 2015.