Lightning detectors were first developed in the 1970s, and the first national network of detectors across the United States went into operation in 1994. These first systems were based on the ground, but in 1995 and 1997 NASA launched two satellites with instrumentation on-board that could measure lightning strikes on Earth from space.
The below information is from Vaisala.
Vaisala Lightning Explorer (image above) displays recent lightning activity across the entire continental U.S. The lightning data displayed is 20 minutes delayed and updated every 20 minutes. Get the latest map available by clicking "Refresh" under the map. The map shows a 2-hour time period with lightning data color coded in 20-minute increments.