Harris became interested in the civic affairs of his adopted community. First he became a member of one of the volunteer fire companies that preceded the establishment of the Metropolitan District paid fire-fighting company in 1865. Later he became active in Democratic Party affairs in New York and was the President of the New York City Board of Education from 1846 to 1848.

As the President of the New York City Board of Education, Harris lobbied the New York State legislature to authorize the expenditure of the Literature Fund administered by the New York State Board of Regents to support a public institution of higher learning in New York. At the time, the Literature Fund was allocated to the University of the City of New York, now New York University, and Columbia College, now Columbia University. He expressed his views in a series of columns written under the pen name of Plain Truth that appeared in The Morning Courier and New York Enquirer. In the column that appeared in the New York Enquirer on March 15, 1847, he stated the following:

No, Sirs, the system now pursued by that excellent society and by our ward schools is the true one, and may be advantageously applied to higher seminaries of learning. Make them the property of the people open the doors to all let the children of the rich and the poor take their seats together and know of no distinction save that of industry, good conduct, and intellect. A large number of the children of the rich now attend our public schools, and the ratio is rapidly increasing.

This was one of a series of columns that were printed between February and March 1847, discussing the idea of a free educational institution. Opposing columns appeared under the pen name Justice, representing the viewpoint of someone affiliated with the University of the City of New York, now New York University.