The Grand Duchy of Oldenburg and the United States began mutual recognition in 1829 but never established formal relations.

Recognition began on December 2, 1829, when U.S. Secretary of State Martin Van Buren issued an exequatur to Frederick A. Mensch Esq.

The declaration was signed by U.S. Special Agent Ambrose Dudley Mann and Oldenburg’s head of Foreign Affairs, W.E.

[2] On December 30, 1853, the Grand Duchy of Oldenburg signed the Declaration of Accession to the Convention for the Extradition of Criminals, Fugitives from Justice, of June 16, 1852, Between the United States and Prussia and Other States of the Germanic Confederation, to establish reciprocal extradition of fugitive criminals in special cases.

[1] This article incorporates public domain material from "A Guide to the United States' History of Recognition, Diplomatic, and Consular Relations, by Country, since 1776: Oldenburg".