At Roxbury in 1846 he opened his first law office, taking comparatively soon a leading position at the Bar.  He there continued his practice until 1865 when he formed with the late Hon. Harvey Jewell and the since associate justice of the Supreme Judicial Court, the Hon. Walbridge A. Field, the famous and successful law firm, having offices at number 5 Tremont street, of Jewell, Gaston and Field.  This firm continued until the election of Mr. Gaston to the gubernatorial chair of Massachusetts in 1874.  He was the Democratic candidate the year previous for this office, his competitor being Mr. Washburn, who was elected but did not long retain the chair of State, being elected to the United States Senate.  At the convention nominating William B. Washburn for Governor there were four other candidates for the honor:  Alexander H. Rice, George B. Loring, Harvey Jewell and Benjamin F. Butler.  The latter created no little unquiet by the zeal and strength of his support.  The upshot was that there was a harmonious combination of the forces of the four contestants of Butler upon Mr. Washburn.  It is remembered that some of the party organs were upon nettles, fearing that General Butler would bolt the nomination, but he came out squarely and declared that as he had staked his issues with the convention he would abide the result.

In the canvass of 1874 Mr. Gaston was opposed by Hon. Thomas Talbot, who, by reason of Governor Washburn’s election to the Senate as stated, was acting as Governor, having been elected Lieutenant Governor on the ticket with Mr. Washburn.  Governor Gaston’s majority over Mr. Talbot was 7,033.  In the following canvass of 1875, Mr. Gaston having been re-nominated by the Democracy, his competitor was Hon. Alexander H. Rice.  By this time, that part of the country represented by the strongly-intrenched Republican party, was fully aroused to the exigency of the hour.  The edict came from the political centre at Washington to the effect that the Republican party could not stand another defeat in Massachusetts, especially on the eve of a presidential campaign.  The national organization concentrated a wonderfully efficient auxiliary force in aid of the intense activity already exerted by the local managers, who so well understood the popularity of Mr. Gaston and of the strong hold he had upon the people.  It seems now that the Democratic managers accepted or anticipated failure as a foregone conclusion, and no great fight was made; otherwise they would probably have won the election, as Mr. Rice was elected by only the small plurality of 5,306 votes.  This is very significant, taken in connection with the fact that General Grant carried Massachusetts in 1872 by 74,212 majority.

In 1876, that memorable year—­memorable as the year of the electoral commission—­Governor Gaston magnanimously declined the re-nomination, which a large majority of the convention was undoubtedly eager to confer.  The nomination of Charles Francis Adams was to the rank and file and to the party managers a disappointment, and the enthusiasm that he was expected to arouse was not materialized.