Question: What is the reason for change when Maryland 6th is the district? 
SQL: SELECT "Reason for change" FROM "1-225100-4" WHERE "District" = 'Maryland 6th';

Question: Who is the vacator when South Carolina 4th is the district?
SQL: SELECT "Vacator" FROM "1-225100-4" WHERE "District" = 'South Carolina 4th';

Question: Who is the successor when Florida Territory At-large is the district?
SQL: SELECT "Successor" FROM "1-225100-4" WHERE "District" = 'Florida Territory At-large';