Read 28 U.S.C. §1331:
The district courts shall have original jurisdiction of all civil actions arising under the Constitution, laws, or treaties of the United States.
The original grant of federal question jurisdiction contained in the Act of 1875 included a provision restricting jurisdiction to cases in which the matter in dispute exceed the value of $500. Over the next century, in response to a concern that the continued expansion of federal statutory claims was congesting federal court dockets, Congress occasionally raised the jurisdictional ante. In 1887, the minimum amount of controversy requirement was augmented to $2000. This was increased to $3000 in 1911 and inflated again to $10,000 in 1958. In 1980, however, Congress reversed direction by abolishing the jurisdictional amount requirement for federal question cases altogether. One reason for the elimination of the jurisdictional amount in controversy was the fact that Congress had enacted a series of additional jurisdictional statutes that conferred subject matter jurisdiction over specialized types of federal claims, such as commerce, antitrust, civil rights, bankruptcy and maritime actions, and none of these statutes included a minimum amount in controversy requirement. See e.g., 28 U.S.C. §1333, 1334, 1337,1338 and 1343. Additionally, the elimination of the amount in controversy requirement in §1331 (sometimes referred to as the “general” federal question jurisdiction statute) was responsive to the frequently asserted concern that the presence of an amount in controversy requirement generated unnecessary and complicated litigation over the value of various statutory and constitutional rights in cases where the plaintiff was not seeking legal relief.
The fact that both the framers of the Constitution and Congress provided federal courts with subject matter jurisdiction over all questions of federal law does not mean that state courts are totally devoid of authority to entertain cases involving federal questions. Unless Congress has provided otherwise, state courts have inherent jurisdiction concurrent with that of the federal courts over claims arising under federal law. In a small minority of areas (including admiralty, antitrust, patent and copyright, and bankruptcy actions), Congress has provided the federal courts with exclusive jurisdiction. But the presumption is against vesting the federal courts with exclusive jurisdiction over federal questions, and the Supreme Court has declared that this presumption can be rebutted only by “an explicit statutory directive, by unmistakable implication from legislative history, or by a clear incompatibility between state-court jurisdiction and federal interests.” Consequently, absent such evidence, the state courts will be deemed to possess concurrent jurisdiction over the federal claim.