When news about the crisis reached Washington and London, officials from both nations were shocked and took action to calm the potentially explosive international incident.
In September, U.S. President James Buchanan sent General Winfield Scott to negotiate with Governor Douglas and resolve the growing crisis. This was in the best interest of the United States, as sectional tensions within the country were increasing, soon to culminate in the Civil War. Scott had calmed two other border crises between the two nations in the late 1830s. He arrived in the San Juans in October and began negotiations with Douglas.
As a result of the negotiations, both sides agreed to retain joint military occupation of the island until a final settlement could be reached, reducing their presence to a token force of no more than 100 men. The "English Camp" was established on the north end of San Juan Island along the shoreline, for ease of supply and access; and the "American Camp" was created on the south end on a high, windswept meadow, suitable for artillery barrages against shipping. Today the Union Jack still flies above the "English Camp", being raised and lowered daily by park rangers, making it one of the few places without diplomatic status where U.S. government employees regularly hoist the flag of another country, though this is for commemoration purposes.
Union Jack at the "English Camp" in San Juan Island National Historical Park During the years of joint military occupation, the small British and American units on San Juan Island had an amicable mutual social life, visiting one another's camps to celebrate their respective national holidays and holding various athletic competitions. Park rangers tell visitors the biggest threat to peace on the island during these years was "the large amounts of alcohol available".
This state of affairs continued for the next 12 years. The dispute was peacefully resolved after more than a decade of confrontation and military bluster, during which time the local British authorities consistently lobbied London to seize back the Puget Sound region entirely, as the Americans were busy elsewhere with the Civil War. In 1866, the Colony of Vancouver Island was merged with the Colony of British Columbia to form an enlarged Colony of British Columbia. In 1871, the enlarged colony joined the newly formed Dominion of Canada. That year, the United Kingdom and the United States signed the Treaty of Washington, which dealt with various differences between the two nations, including border issues involving the newly formed Dominion. Among the results of the treaty was the decision to resolve the San Juan dispute by international arbitration, with German Emperor Wilhelm I chosen to act as arbitrator. Wilhelm referred the issue to a three-man arbitration commission which met in Geneva for nearly a year. On October 21, 1872, the commission decided in favor of the United States. The arbitrator chose the American-preferred marine boundary via Haro Strait, to the west of the islands, over the British preference for Rosario Strait which lay to their east.
British troops evacuate San Juan Island On November 25, 1872, the British withdrew their Royal Marines from the British Camp. The Americans followed by July 1874.
Canadian politicians and public, already angry with the Oregon Treaty, were once again upset that Britain had not looked after their interests, and Canada sought greater autonomy in international affairs.
The Pig War is commemorated in San Juan Island National Historical Park.