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:
| Representative | Title | From | To | Appointed by |
| --- | --- | --- | --- | --- |
| William Shaler | Special Diplomatic Agent | 1810 | 1812 | James Madison |
| John H. Robinson | Special Diplomatic Agent | 1812 | 1814 | James Madison |
| Joel Roberts Poinsett | Minister | 1825 | 1829 | John Quincy Adams |
| Anthony Butler | Special Diplomatic Agent | 1829 |  |  |
| Anthony Butler | Chargé d'Affaires | 1829 | 1835 |  |
| William A. Slacum | Special Diplomatic Agent | 1835 | 1836 | Andrew Jackson |
| Powhatan Ellis | Chargé d'Affaires | 1836 |  | Andrew Jackson |
| Robert Greenhow | Special Diplomatic Agent | 1837 |  |  |
| Powhatan Ellis | Minister | 1839 | 1842 | Martin Van Buren |
| Henry E. Lawrence | Special Diplomatic Agent | 1842 |  | John Tyler |
| Waddy Thompson, Jr. | Minister | 1842 | 1844 | John Tyler |
| Moses Yale Beach | Special Diplomatic Agent | 1843 |  | John Tyler |
| Gilbert L. Thompson | Special Diplomatic Agent | 1844 |  | John Tyler |
| Wilson Shannon | Minister | 1844 | 1845 | John Tyler |
| John Slidell | Minister | 1845 |  | James K. Polk |
| David Conner | Special Diplomatic Agent | 1846 |  | James K. Polk |
| Nathan Clifford | Minister | 1848 | 1849 | James K. Polk |
| Robert P. Letcher | Minister | 1849 | 1852 |  |
| Robert Greenhow | Special Diplomatic Agent | 1850 |  |  |
| George G. Goss | Special Diplomatic Agent | 1850 | 1852 |  |
| George W. Slacum | Special Diplomatic Agent | 1851 |  | Millard Fillmore |
| Edward Smith | Special Diplomatic Agent | 1852 |  | Millard Fillmore |
| Alfred Conkling | Minister | 1852 | 1853 | Millard Fillmore |
| George E. Cooper | Special Diplomatic Agent | 1853 |  |  |
| Christopher L. Ward | Special Diplomatic Agent | 1853 |  |  |
| James Gadsden | Minister | 1853 | 1856 |  |
| Richard S. Spofford | Special Diplomatic Agent | 1854 |  | Franklin Pierce |
| John Forsyth Jr. | Minister | 1856 | 1858 | Franklin Pierce |
| William M. Churchwell | Special Diplomatic Agent | 1858 |  | James Buchanan |
| Alfred Mordecai | Special Diplomatic Agent | 1858 |  | James Buchanan |
| Duff Green | Special Diplomatic Agent | 1859 |  | James Buchanan |
| David R. Porter | Special Diplomatic Agent | 1859 |  | James Buchanan |
| Robert Milligan McLane | Minister | 1859 | 1860 | James Buchanan |
| Henry Roy de la Reintrie | Special Diplomatic Agent | 1860 |  | James Buchanan |
| John B. Weller | Minister | 1860 | 1861 | James Buchanan |
| Thomas Corwin | Minister | 1861 | 1864 |  |
| Robert W. Shufelt | Special Diplomatic Agent | 1862 |  | Abraham Lincoln |
| Lewis D. Campbell | Minister | 1866 | 1867 | Andrew Johnson |
| Marcus Otterbourg | Minister | 1867 |  | Andrew Johnson |
| William S. Rosecrans | Minister | 1868 | 1869 | Andrew Johnson |
| Thomas H. Nelson | Minister | 1869 | 1873 |  |
| John W. Foster | Minister | 1873 | 1880 | Ulysses S. Grant |
| Philip Hicky Morgan | Minister | 1880 | 1885 | Rutherford B. Hayes |
| Henry R. Jackson | Minister | 1885 | 1886 |  |
| Thomas Courtland Manning | Minister | 1886 | 1887 | Grover Cleveland |
| Edward S. Bragg | Minister | 1888 | 1889 | Grover Cleveland |
| Thomas Ryan | Minister | 1889 | 1893 |  |
| Isaac P. Gray | Minister | 1893 | 1895 |  |
| Matt Whitaker Ransom | Minister | 1895 | 1897 | Grover Cleveland |
| Powell Clayton | Minister | 1897 | 1898 |  |
Question:
who was the first ambassador the united states has sent to mexico?
Answer:
William Shaler