Marks was also involved in numerous local organisations including the Presbyterian Church, Aboriginal Protection Board and Agricultural Society.
[3] In 1856 Marks was elected as one of the two members for East Camden in the first New South Wales Legislative Assembly under responsible government.
He did not stand as a candidate when his electorate was abolished before the 1859 election and he declined Cowper's invitation to join the Legislative Council in 1861.
In this position he was responsible for ensuring the passage of government legislation, including a contentious land bill, through the upper house.
Marks lost the position when Farnell's government fell in December 1878 but he continued to attend the Legislative Council until his death.