district                   vacator                                    reason for change                         successor         date successor seated
0   colorado territory at - large                  new seat                                             new seat  hiram p bennett (conservative r)              august 19 , 1861
1     nevada territory at - large                  new seat                                             new seat                  john cradlebaugh             december 2 , 1861
2     dakota territory at - large                  new seat                                             new seat                 john b s todd (d)             december 9 , 1861
3                   louisiana 1st                    vacant                                               vacant           benjamin f flanders (u)             december 3 , 1862
4                   louisiana 2nd                    vacant                                               vacant                  michael hahn (u)             december 3 , 1862
5                    virginia 1st                    vacant                                               vacant                joseph e segar (u)                  may 6 , 1862
6                    virginia 7th                    vacant                                               vacant               charles h upton (u)                 july 4 , 1861
7                       ohio 13th          john sherman (r)     resigned march 12 , 1861 when elected us senator            samuel t worcester (r)                 july 4 , 1861
8               pennsylvania 12th     george w scranton (r)                                 died march 24 , 1861             hendrick b wright (d)                 july 4 , 1861
9               oregon at - large       andrew j thayer (d)   election was successfully contested july 30 , 1861                george k shiel (d)                july 30 , 1861
10              massachusetts 5th     william appleton (cu)   resigned september 27 , 1861 due to failing health                 samuel hooper (r)             december 2 , 1861
11                   kentucky 1st       henry c burnett (d)  expelled december 3 , 1861 for support of secession                samuel l casey (u)               march 10 , 1862
12                   kentucky 2nd       james s jackson (u)  resigned december 13 , 1861 to enter the union army               george h yeaman (u)             december 1 , 1862
13                   virginia 7th       charles h upton (u)     declared not entitled to seat february 27 , 1862                lewis mckenzie (u)            february 16 , 1863
14                   illinois 9th          john a logan (d)      resigned april 2 , 1862 to enter the union army               william j allen (d)                 june 2 , 1862
15               pennsylvania 7th       thomas b cooper (d)                                  died april 4 , 1862                 john d stiles (d)                 june 3 , 1862
16              massachusetts 9th    goldsmith f bailey (r)                                    died may 8 , 1862                  amasa walker (r)             december 1 , 1862
17                   missouri 1st  francis p blair , jr (r)   resigned july 1862 to become colonel in union army                            vacant  vacant for remainder of term

Table as JSON:
{"district":{"0":"colorado territory at - large","1":"nevada territory at - large","2":"dakota territory at - large","3":"louisiana 1st","4":"louisiana 2nd","5":"virginia 1st","6":"virginia 7th","7":"ohio 13th","8":"pennsylvania 12th","9":"oregon at - large","10":"massachusetts 5th","11":"kentucky 1st","12":"kentucky 2nd","13":"virginia 7th","14":"illinois 9th","15":"pennsylvania 7th","16":"massachusetts 9th","17":"missouri 1st"},"vacator":{"0":"new seat","1":"new seat","2":"new seat","3":"vacant","4":"vacant","5":"vacant","6":"vacant","7":"john sherman (r)","8":"george w scranton (r)","9":"andrew j thayer (d)","10":"william appleton (cu)","11":"henry c burnett (d)","12":"james s jackson (u)","13":"charles h upton (u)","14":"john a logan (d)","15":"thomas b cooper (d)","16":"goldsmith f bailey (r)","17":"francis p blair , jr (r)"},"reason for change":{"0":"new seat","1":"new seat","2":"new seat","3":"vacant","4":"vacant","5":"vacant","6":"vacant","7":"resigned march 12 , 1861 when elected us senator","8":"died march 24 , 1861","9":"election was successfully contested july 30 , 1861","10":"resigned september 27 , 1861 due to failing health","11":"expelled december 3 , 1861 for support of secession","12":"resigned december 13 , 1861 to enter the union army","13":"declared not entitled to seat february 27 , 1862","14":"resigned april 2 , 1862 to enter the union army","15":"died april 4 , 1862","16":"died may 8 , 1862","17":"resigned july 1862 to become colonel in union army"},"successor":{"0":"hiram p bennett (conservative r)","1":"john cradlebaugh","2":"john b s todd (d)","3":"benjamin f flanders (u)","4":"michael hahn (u)","5":"joseph e segar (u)","6":"charles h upton (u)","7":"samuel t worcester (r)","8":"hendrick b wright (d)","9":"george k shiel (d)","10":"samuel hooper (r)","11":"samuel l casey (u)","12":"george h yeaman (u)","13":"lewis mckenzie (u)","14":"william j allen (d)","15":"john d stiles (d)","16":"amasa walker (r)","17":"vacant"},"date successor seated":{"0":"august 19 , 1861","1":"december 2 , 1861","2":"december 9 , 1861","3":"december 3 , 1862","4":"december 3 , 1862","5":"may 6 , 1862","6":"july 4 , 1861","7":"july 4 , 1861","8":"july 4 , 1861","9":"july 30 , 1861","10":"december 2 , 1861","11":"march 10 , 1862","12":"december 1 , 1862","13":"february 16 , 1863","14":"june 2 , 1862","15":"june 3 , 1862","16":"december 1 , 1862","17":"vacant for remainder of term"}}