Underlying the popular sentiment, which might have evaporated in time, which forced the United States to take up arms against Spanish rule in Cuba, were our economic relations with the West Indies and the South American republics… The Spanish-American War was but an incident of a general movement of expansion which had its roots in the changed environment of an industrial capacity far beyond our domestic powers of consumption. It was seen to be necessary for us not only to find foreign purchasers for our goods, but to provide the means of making access to foreign markets easy, economical and safe.

American labor unions had sympathy for the Cuban rebels as soon as the insurrection against Spain began in 1895. But they opposed American expansionism. Both the Knights of Labor and the American Federation of Labor spoke against the idea of annexing Hawaii, which McKinley proposed in 1897. Despite the feeling for the Cuban rebels, a resolution calling for U.S. intervention was defeated at the 1897 convention of the AFL. Samuel Gompers of the AFL wrote to a friend: "The sympathy of our movement with Cuba is genuine, earnest, and sincere, but this does not for a moment imply that we are committed to certain adventurers who are apparently suffering from Hysteria…"

When the explosion of the Maine in February led to excited calls for war in the press, the monthly journal of the International Association of Machinists agreed it was a terrible disaster, but it noted that the deaths of workers in industrial accidents drew no such national clamor. It pointed to the Lattimer Massacre of September 10, 1897, during a coal strike in Pennsylvania. Miners marching on a highway to the Lattimer mine — Austrians, Hungarians, Italians, Germans — who had originally been imported as strikebreakers but then organized themselves, refused to disperse, whereupon the sheriff and his deputies opened fire, killing nineteen of them, most shot in the back, with no outcry in the press. The labor journal said that the

… carnival of carnage that takes place every day, month and year in the realm of industry, the thousands of useful lives that are annually sacrificed to the Moloch of greed, the blood tribute paid by labor to capitalism, brings forth no shout for vengeance and reparation… Death comes in thousands of instances in mill and mine, claims his victims, and no popular uproar is heard.

The official organ of the Connecticut AFL, The Craftsman, also warned about the hysteria worked up by the sinking of the Maine:

A gigantic… and cunningly-devised scheme is being worked ostensibly to place the United States in the front rank as a naval and military power. The real reason is that the capitalists will have the whole thing and, when any workingmen dare to ask for the living wage… they will be shot down like dogs in the streets.

Some unions, like the United Mine Workers, called for U.S. intervention after the sinking of the Maine. But most were against war. The treasurer of the American Longshoremen's Union, Bolton Hall, wrote "A Peace Appeal to Labor," which was widely circulated:

If there is a war, you will furnish the corpses and the taxes, and others will get the glory. Speculators will make money out of it — that is, out of you. Men will get high prices for inferior supplies, leaky boats, for shoddy clothes and pasteboard shoes, and you will have to pay the bill, and the only satisfaction you will get is the privilege of hating your Spanish fellow-workmen, who are really your brothers and who have had as little to do with the wrongs of Cuba as you have.

Socialists opposed the war. One exception was the Jewish Daily Forward. The People, newspaper of the Socialist Labor party, called the issue of Cuban freedom "a pretext" and said the government wanted war to "distract the attention of the workers from their real interests." The Appeal to Reason, another Socialist newspaper, said the movement for war was "a favorite method of rulers for keeping the people from redressing domestic wrongs." In the San Francisco Voice of Labor a Socialist wrote: "It is a terrible thing to think that the poor workers of this country should be sent to kill and wound the poor workers of Spain merely because a few leaders may incite them to do so."

But after war was declared, Foner says, "the majority of the trade unions succumbed to the war fever." Samuel Gompers called the war "glorious and righteous" and claimed that 250,000 trade unionists had volunteered for military service. The United Mine Workers pointed to higher coal prices as a result of the war and said: "The coal and iron trades have not been so healthy for some years past as at present."

The war brought more employment and higher wages, but also higher prices. Foner says: "Not only was there a startling increase in the cost of living, but, in the absence of an income tax, the poor found themselves paying almost entirely for the staggering costs of the war through increased levies on sugar, molasses, tobacco, and other taxes…" Gompers, publicly for the war, privately pointed out that the war had led to a 20 percent reduction of the purchasing power of workers' wages.

On May Day, 1898, the Socialist Labor party organized an antiwar parade in New York City, but the authorities would not allow it to take place, while a May Day parade called by the Jewish Daily Forward, urging Jewish workers to support the war, was permitted. The Chicago Labor World said: "This has been a poor man's war — paid for by the poor man. The rich have profited by it, as they always do…"

The Western Labor Union was founded at Salt Lake City on May 10, 1898, because the AFL had not organized unskilled workers. It wanted to bring together all workers "irrespective of occupation, nationality, creed or color" and "sound the death knell of every corporation and trust that has robbed the American laborer of the fruits of his toil…" The union's publication, noting the annexation of Hawaii during the war, said this proved that "the war which started as one of relief for the starving Cubans has suddenly changed to one of conquest."

The prediction made by longshoreman Bolton Hall, of wartime corruption and profiteering, turned out to be remarkably accurate. Richard Morris's Encyclopedia of American History gives startling figures:

Of the more than 274,000 officers and men who served in the army during the Spanish-American War and the period of demobilization, 5,462 died in the various theaters of operation and in camps in the U.S. Only 379 of the deaths were battle casualties, the remainder being attributed to disease and other causes.

The same figures are given by Walter Millis in his book The Martial Spirit. In the Encyclopedia they are given tersely, and without mention of the "embalmed beef" (an army general's term) sold to the army by the meatpackers — meat preserved with boric acid, nitrate of potash, and artificial coloring matter.

In May of 1898, Armour and Company, the big meatpacking company of Chicago, sold the army 500,000 pounds of beef which had been sent to Liverpool a year earlier and had been returned. Two months later, an army inspector tested the Armour meat, which had been stamped and approved by an inspector of the Bureau of Animal Industry, and found 751 cases containing rotten meat. In the first sixty cases he opened, he found fourteen tins already burst, "the effervescent putrid contents of which were distributed all over the cases." (The description comes from the Report of the Commission to Investigate the Conduct of the War Department in the War with Spain, made to the Senate in 1900.) Thousands of soldiers got food poisoning. There are no figures on how many of the five thousand noncombat deaths were caused by that.

The Spanish forces were defeated in three months, in what John Hay, the American Secretary of State, later called a "splendid little war." The American military pretended that the Cuban rebel army did not exist. When the Spanish surrendered, no Cuban was allowed to confer on the surrender, or to sign it. General William Shafter said no armed rebels could enter the capital city of Santiago, and told the Cuban rebel leader, General Calixto Garcia, that not Cubans, but the old Spanish civil authorities, would remain in charge of the municipal offices in Santiago.