In 1852 the town of Lafayette in Jefferson Parish agreed to unite with the three New Orleans municipalities, and a new charter was put into effect. This charter provided for a bicameral council composed of two boards: a Board of Alderman and a Board of Assistant Alderman.The Board of Alderman consisted of 10-13 members serving 1-2 year terms, while the Assistant Alderman numbered 20-27 and served 1 year terms. Both councils were eleceted based on number of voters within their districts. The Board of Alderman were representative of the municipal distircits (the same area as the former municipalities pls the City of Lafayette) and the Assistant Alderman were representative of individual wards within the municipal districts. The boards met separately but their legislative powers were the same. The only officeholders who were elected by city-wide vote were the mayor and four of the department heads, all of whom were chosen for two-year terms. The mayor had the veto power but it could be overridden by a three-fifths vote of the council.

The 1852 city charter provided that each Board of the Common Council could originate, amend, concur in, or reject any ordinance or resolution. No such law would take effect, however, until it had passed both Boards. Ordinances levying a tax, making an appropriation of over $1,000, or providing for the purchase of real estate had to be passed by a majority of the members elected to each Board, not merely by a majority of members present at a given meeting. These laws, once passed by both Boards of the Council, were to be transmitted to the Mayor for his consideration. If he approved of the act he was to sign it and return it to the Council, and it would have the effect of law. If he did not approve of it, the Mayor had five days to return it to the Council with his objections, otherwise the legislation would gain the effect of law. The mayor had veto power but it could be overridden by a three-fifths vote of the council. The Mayor had the responsibility of seeing that all ordinances and resolutions passed by the Common Council were published in the newspaper selected by the Council.

City government was suspended following the Federal capture of New Orleans during the Civil War in 1862 and did not resume until the end of the occupation period in 1866. The legislative branch of New Orleans municipal government has operated under several official designations since 1866. The Board of Alderman and Assistant Alderman remained in place until the Charter of 1870, which established a seven member elected council. Following 1870, all records of the city councils are described together under the records of the New Orleans City Council.