So—what was the largest lamp ever made by 1899 and to what purpose was it used? The answer can be found in the American Electrician, Vol XI, No 7, Jul 1899, pg 340. In general, very large incandescent lamps were not made because arc lamps would usually better fill the need. However, there was a need for an incandescent lamp, rather than an arc lamp, for application in lighthouses. Such a lamp is shown in the photo below.

The reason an incandescent lamp served the need of a lighthouse better than an arc lamp was "its greater fog penetration, the yellower rays of the glowing filament being dampened out and absorbed to a much less extent than the rays of an arc light."

The Bryan-Marsh Company experimented with large lamps, the largest one rated at 5000 candlepower. The lamp contained the standard double-filament type. The filaments were connected in parallel and operated at 236 volts. The power consumed was about 15 kilowatts at 60 amperes. This lamp burned out after being exhibited for three nights at an Electrical Show. It had been burned in the base up position and the heat softened the glass at the base. The cost of construction and erection of this lamp was over $1000.