"I consider this among the most important acts of my life, second only to my signing the Declaration of Independence, if even it be second to that."

So stated Charles Carroll of Carrolton, the leading citizen of Baltimore and Maryland and perhaps the wealthiest man in America, on July 4, 1828.

At least that's now contemporary history records the Carroll quotation as he turned the symbolic first spade of earth to start construction of the Baltimore & Ohio, America's first major railroad.

It may be easy to quarrel with Carroll's purported statement that inauguration of a railroad could be of secondary importance to the Declaration of Independence.But there is no question that railroad transportation in subsequent years helped the nation grow and to keep it united.

The historic beginning of the B&O actually took place 150 years ago next Monday and more than 350 business, labor and government leaders will gather there on Monday night for a birthday party. Earlier Monday, a reproduction of Peter Cooper's Tom Thumb - the first U.S.-built locomotive to operate regular service - will restage a race with a horse, first run in 1830.

Although the horse won in the 19th Century, when a belt slipped off a pulley on the Tom Thumb, the locomotive soon proved itself.

Maryland's legislature had chartered the B&O on Feb. 28, 1827, at a time when the nation's population was 12 million and there were more people living west of the Allegheny Mountains than had lived in the first 13 states in George Washington's time.

Business and civic leaders in Eastern cities were anxious to maintain or establish commercial ties to the West. Toll roads had been built and canals were dug but the natural method for commerce between the Midwest and Europe was by water - using the rivers of New Orleans and abroad.

New Yorkers built the Erie Canal in 1825 to tap the Midwest commerce and leaders of Baltimore began to panic when plans were announced for the Chesapeake and Ohio Canal along the Potomac River, making Georgetown the terminal and bypassing Baltimore.

Bankers and other businessmen in Baltimore, eyeing the initial success of a railroad in England, decided that the only way to keep their port thriving would be a railroad link to the West. A committee of 25 was formed on Feb. 2, 1827. With unusual speed for any committee, a recommendation for a 380-mile link to the Ohio River was endorsed and a character application filed within weeks.

Stock was put on sale in Baltimore, Frederick and Hagerstown and quickly was sold out; the State of Maryland itself purchased $500.000 of the issue. Charles Carroll joined the initial board.

The rest is history: B&O began operations on Jan. 30, 1830, carrying revenue-paying passengers; the road reached to Ellicott City (then Ellicott's Mills) in May of that year; a Baltimore-Washington line opened in 1835; and it reached the Ohio River in 1852. Later, the B&O's routes rtached to St. Louis Chicago and New Jersey - with 11,000 miles of track in 13 states.

Today, the B&O is part of the Chessie System, Inc., one of the nation's largest railroad-based conglomerates. Chessie also owns the Chesapeake & Ohio and Western Maryland railroads, the Greenbrier Hotel, and extensive real estate, mining and timber holdings, with annual revenues of $1.45 billion.

Monday's birthday celebration, portrayed by the Association of American Railroads as the rail industry's 150th anniversary, will be held at the B&O Railroad Museum, adjacent to Mt. Clare station, the nation's first railroad station.