
142 U.S. 615 (1892)
UNITED STATES
v.
ALABAMA GREAT SOUTHERN RAILROAD COMPANY.
No. 749.
Supreme Court of United States.
Submitted January 8, 1892.
Decided January 18, 1892.
APPEAL FROM THE COURT OF CLAIMS.
*618 Mr. Assistant Attorney General Parker for appellant.
Mr. M.D. Brainard, Mr. Charles King and Mr. William B. King for appellee.
*619 MR. JUSTICE BROWN, after stating the case, delivered the opinion of the court.
This case depends upon the construction to be given to section 13 of the act of July 12, 1876, which reads as follows: "Section 13. That railroad companies whose railroad was constructed in whole or in part by a land grant made by Congress on the condition that the mails should be transported over their road at such price as Congress should by law direct, shall receive only eighty per centum of the compensation authorized by this act." As it is admitted that the construction of so much of this road as lay within the States of Alabama and Mississippi, amounting to 263.85 miles, was aided by the proceeds of lands granted by the acts of Congress of June 3, 1856, 11 Stat. 17, c. 41, and August 11, 1856, 11 Stat. 30, c. 83, and the residue of such road lying within the States of Tennessee and Georgia, amounting to 31.6 miles, was constructed without such aid, the question is presented whether the government is entitled to the transportation of the mail over the whole of such road at eighty per cent of the compensation provided for roads which have received no aid from Congress, or whether such percentage applies only to so much of the road as lies within the States of Alabama and Mississippi.
The difficulty arises from the fact that, by section 13, above *620 quoted, all roads "constructed in whole or in part" by Congressional land grants are bound to carry at the reduced rates. These words, however, are susceptible of several constructions. They may mean such roads as received grants of land the proceeds of whose sale were sufficient to pay the entire or only the partial cost of their construction. In this case the language would be confined to the linear parts of such roads as receive the aid of the land grants,  in the case under consideration, only that part of the road lying in Alabama or Mississippi. Or they may mean that railroads, any linear part of which received the aid of a land grant of Congress in its construction, should be bound to carry the mails at a reduced rate over the entire line. This, which is doubtless the literal reading of the statute, supports the contention of the government in this case. As applied to the particular facts of the present case, this interpretation of the statute would work no great hardship, since the unaided part of the road was but little more than ten per cent of the entire line; but, if the case were reversed, and the aided part amounted only to ten per cent of the entire road, it would be equally within the words of the statute, and the injustice of the construction would become clearly apparent, especially in the case put in the opinion of the learned judge of the court below, if there were a parallel rival road, unaided by a Congressional grant, receiving the full compensation allowed by law. It would also result from this, that if there were two separate roads forming a continuous line, one of which was aided and the other unaided by a land grant, each receiving its appropriate compensation, and these roads were subsequently consolidated, the aided portion would draw after it its own compensation at the reduced rate, and would compel it to be applied to the whole line.
But these words are still susceptible of a third construction, viz., that any railroad the entire line of which or only certain linear portions of which had been constructed by a Congressional land grant, should receive the reduced rate properly proportioned to the part which had received such aid; and that, as to the unaided portion, it should receive the full compensation *621 allowed by law. This was the construction given to it by the Postmaster General and by the accounting officers of the Treasury at the time the act was passed, and the Alabama and Chattanooga Railroad Company and its successor, the appellee, was, and continued to be, paid upon that basis from 1876 to 1885, by six Postmasters General, when in 1885, the then incumbent of the office reversed the rulings of his predecessors, and not only subjected the entire line to the reduced rates, but made such construction retroactive, and enforced repayment of what the road had for nine years received under the prior construction.
We think the contemporaneous construction thus given by the executive department of the government, and continued for nine years through six different administrations of that department  a construction which, though inconsistent with the literalism of the act, certainly consorts with the equities of the case  should be considered as decisive in this suit. It is a settled doctrine of this court that, in case of ambiguity, the judicial department will lean in favor of a construction given to a statute by the department charged with the execution of such statute, and, if such construction be acted upon for a number of years, will look with disfavor upon any sudden change, whereby parties who have contracted with the government upon the faith of such construction may be prejudiced. It is especially objectionable that a construction of a statute favorable to the individual citizen should be changed in such manner as to become retroactive, and to require from him the repayment of moneys to which he had supposed himself entitled, and upon the expectation of which he had made his contracts with the government. These principles were announced as early as 1827 in Edwards' Lessee v. Darby, 12 Wheat. 206, 210, and have been steadily adhered to in subsequent decisions. United States v. State Bank of North Carolina, 6 Pet. 29, 39; United States v. Macdaniel, 7 Pet. 1; Brown v. United States, 113 U.S. 568; United States v. Moore, 95 U.S. 760, 763.
The construction we have given to this act is also in harmony with that given to the Pacific Railroad Act of 1862 in United *622 States v. Kansas Pacific Railway Co., 99 U.S. 455, and the Thurman Act of May 7, 1878, in United States v. Central Pacific Railroad Company, 118 U.S. 235.
There was no error in the judgment of the Court of Claims, and it is, therefore,
Affirmed.
