A number of factors combined to make the decision clear.
League said circulation for The Daily Mail - the more local, homier Washington County paper, which wished readers "Good afternoon!" on the front page - has steadily declined, part of a pronounced nationwide trend that has killed many evening newspapers.
At the same time, circulation has risen for The Morning Herald, which covers parts of West Virginia and Pennsylvania, along with Washington County.
In September 1989, The Morning Herald's circulation was 21,468, a shade more than The Daily Mail's, which was 21,062.
By September 2006, circulation was 22,719 for The Morning Herald and 12,599 for The Daily Mail.
League said Schurz Communications Inc., which owns The Herald-Mail Co., let The Daily Mail hang on for as long as it could, to serve readers.
In 1950, there were 1,450 evening papers and 322 morning papers in the country, according to Editor & Publisher magazine figures supplied by the Newspaper Association of America.
By 2000, morning papers had passed evening papers, 766 to 727, and their lead has grown since then.
Demographics and lifestyle changes have worked against evening papers, said John Murray, NAA's vice president of circulation marketing.
Coming home from the plant late in the afternoon and sitting down with the day's news has become increasingly rare in many cities, he said.
Now, with more two-income households, people leave the house early and get home late, Murray said.
Viewership of evening TV network news shows has diminished, too.
"We're watching a total media realignment," League said.
It's highly unusual that The Daily Mail and The Morning Herald coexisted for so long.
Editor & Publisher's 2005 newspaper industry encyclopedia lists 45 U.S. cities with more than one daily newspaper.
In six of those cities, one company publishes separate morning and evening editions. After Monday, when The Herald and The Mail merge, that number will be five.
Scranton, Pa., was on the list until 2005, when it merged its papers into a single morning edition.
Another six cities on the list still have what is known as a joint operating agreement between a morning paper and an evening paper; the papers are editorially separate, but combine their business operations.
League said the surging popularity of getting news on the Internet has been another powerful influence.
The Herald-Mail Co.'s Web site grew more than 100 percent this past year in visitors and in page views, he said.
A Herald-Mail summary shows 1,072,000 visits to the Web site in August 2007, compared to 484,000 visits in August 2006.
"And we didn't have the resources to address that," League said.
Without an evening paper to produce, the newsroom will reorganize. Some staff members will take new jobs focusing on the Web site and keeping it current.
The merger will have virtually no effect on advertisers, Advertising Director Michael Browning said.
Subscribers' biggest concern has been keeping their current carriers, Circulation Director Dwight Rauch said. One reader sent in a petition with 50 names in support of a carrier.
The merger makes sense for delivery, Rauch said. With two sets of people delivering two sets of papers each day, "we are paying our carriers twice to deliver (on) the same block," he said.
The Herald-Mail Co. also will save money on newsprint, negatives and plates by printing one newspaper instead of two, League said.
He said he has heard two main questions from readers.
Will my comics still be there? (Yes)
Will the price change? (No)
When they hear that, according to League, readers conclude: "Well, I support you. Good luck."
Headlee said he's heard a third question from Daily Mail readers: Will West Coast sports scores still get in the paper? (We will do our best to get them in the final editions.)
With The Morning Herald picking up some of The Daily Mail's features in recent years, the papers have become more similar. Long gone are the days of two reporting staffs competing with each other in the same newsroom.
Tradition, though, remains.