Where was the annual Congress session held in December 1916?

Lucknow

At the annual Congress, held in Lucknow in December 1916, Mahatma Gandhi was approached by a peasant from Champaran in Bihar, who told him about the harsh treatment of peasants by British indigo planters.  Mahatma Gandhi was to spend much of 1917 in Champaran, seeking to obtain the peasant's security of tenure as well as the freedom to cultivate the crops of their choice. The following year, 1918, Gandhiji was involved in two campaigns in his home state of Gujarat. First, he intervened in a labour dispute in Ahmedabad, demanding better working conditions for the textile mill workers. Then he joined peasants in Kheda in asking the state for the remission of taxes following the failure of their harvest.