Why was the u. s presidential election of 1876 unusual

The 1876 U.S presidential election was unusual because it marked the most controversial election ever held.  In this election, Samuel Tilden was ahead of his opponent, Rutherford Hayes. However, Hayes was declared the winner based on 20 uncounted votes thus making the results of the election disputable. 

These islands/chinampas then provided rich soil for crops with easy access to water. i hope this is correct, im so sorry if its not !