Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| District | Incumbent | Party | First elected | Result |
| --- | --- | --- | --- | --- |
| Pennsylvania 1 | Thomas B. Florence | Democratic | 1848.0 | Retired Democratic Hold |
| Pennsylvania 2 | Edward J. Morris | People's | 1856.0 | Re-elected Republican Gain |
| Pennsylvania 3 | John P. Verree | People's | 1858.0 | Re-elected Republican Gain |
| Pennsylvania 4 | William Millward | People's | 1858.0 | Retired Republican Gain |
| Pennsylvania 5 | John Wood | People's | 1858.0 | Retired Republican Gain |
| Pennsylvania 6 | John Hickman | Democratic | 1856.0 | Re-elected Republican Gain |
| Pennsylvania 7 | Thomas Corwin | Republican | 1858.0 | Re-elected |
| Pennsylvania 8 | Jacob K. McKenty | Democratic | 1860.0 | Retired Democratic hold |
| Pennsylvania 9 | Thaddeus Stevens | People's | 1858.0 | Re-elected Republican Gain |
| Pennsylvania 10 | John W. Killinger | People's | 1858.0 | Re-elected Republican Gain |
| Pennsylvania 11 | James H. Campbell | People's | 1858.0 | Re-elected Republican gain |
| Pennsylvania 12 | George W. Scranton | People's | 1858.0 | Re-elected Republican gain |
| Pennsylvania 13 | William H. Dimmick | Democratic | 1856.0 | Retired Democratic hold |
| Pennsylvania 14 | Galusha A. Grow | People's | 1850.0 | Re-elected Republican gain |
| Pennsylvania 15 | James Tracy Hale | People's | 1858.0 | Re-elected Republican gain |
| Pennsylvania 16 | Benjamin F. Junkin | People's | 1858.0 | Defeated Democratic gain |
| Pennsylvania 17 | Edward McPherson | People's | 1858.0 | Re-elected Republican gain |
| Pennsylvania 18 | Samuel S. Blair | People's | 1858.0 | Re-elected Republican gain |
| Pennsylvania 19 | John Covode | People's | 1854.0 | Re-elected Republican gain |
| Pennsylvania 20 | William Montgomery | Democratic | 1856.0 | Retired Democratic Hold |
| Pennsylvania 21 | James K. Moorhead | People's | 1858.0 | Re-elected Republican gain |
| Pennsylvania 22 | Robert McKnight | People's | 1858.0 | Re-elected Republican gain |
| Pennsylvania 23 | William Stewart | People's | 1856.0 | Retired Republican gain |
| Pennsylvania 24 | Chapin Hall | People's | 1858.0 | Retired Republican gain |
| Pennsylvania 25 | Elijah Babbitt | People's | 1858.0 | Re-elected Republican gain |
Question:
Which First elected is the lowest one that has an Incumbent of william stewart?
Answer:
1856.0