In 1890, the Lighthouse Board requested $60,000 to construct a light at the mouth of the Magothy River to mark the entrance of the "New Cut-off Channel" to Baltimore. The Board stated that "On account of the impressible character of the shoal, and the liability to destruction or damage by fields of moving ice, no lighthouse, other than an expensive one, can be made permanent."

The assessment was correct - the lighthouse proved quite expensive. Borings made at the selected site revealed a layer of soft mud 55 feet deep below the surface. No caisson had ever been sunk so deep as would be required for this lighthouse. An additional $60,000 was requested. The lone initial bid for the construction contract was nearly $200,000, and was rejected. Bidding was re-opened, and in 1904, Flaherty and Lande received the contract.

To build a lighthouse on the selected site, the contractors built the world's largest caisson. The wooden portion was 48 feet in diameter and 23 feet high. It contained over one million feet of lumber and weighed 972 tons. On completion, the entire caisson, including the cast iron panels, would be 86 feet high.

The caisson was towed to the site on September 19, 1904. The contractors estimated two days of clear weather was needed to anchor the caisson. Unfortunately, heavy seas on the 21st filled the caisson and caused it to settle seven feet out of level. The contractors returned on October 7th, and filled the high side of the caisson with concrete in an attempt to restore the caisson to level. Their efforts were to no avail - on October 12th, a storm turned the entire caisson on its side.

The contractors abandoned the project, and were sued by the government. In 1905, the insurance company took up the project of restoring the caisson. A pier was built around the lighthouse, complete with workers quarters, storage, machinery, a derrick, and even an artesian well. Counterweights were used to bring the caisson to 35 degrees from vertical. Pumping out mud and adding 80 tons of stone to the high side gradually restored the caisson to level. Once the caisson was level, the greatest difficulties had been overcome. The lighthouse finally went into service on October 1, 1908.

Baltimore lighthouse was the world's first atomic-powered lighthouse in 1964. A 60-watt generator the size of a 55-gallon drum, powered by Strontium-90, would provide 10 years of continuous power without refueling. The experiment lasted only two years, and the generator was removed.

The Baltimore light was in poor condition when the Coast Guard arrived to perform repairs on the light (now automated) in 1983. Portholes had left the interior exposed to weather and birds. The roof was leaking. The lens was damaged by bullets. The interior had been damaged by fire and termites. Repairs were made to the lighthouse in 1983 and again in 1989-1990. Milton Hartwig, a former Coast Guardsman who ran the maintenance division of the Coast Guard facility in Baltimore, researched the plans of the lighthouse. When repairing the roof, he restored the dormers to the state where it appears exactly as it did when it went into service in 1908.

References (see links)

Bay Beacons, Turbyville pp. 32-35
The Lighthouses of the Chesapeake, de Gast p. 87
Lighting the Bay: Tales of Chesapeake Lighthouses, Vojtech pp. 71, 79-80, 137-138