Complex sentence: By the end of the 1980s, exchanges on both sides of the Potomac River were running out of numbers; the only way to free up numbers was to end the partial overlay arrangement, a decision that was made in 1991.
Split into simpler sentences: By the end of the 1980s, exchanges on both sides of the Potomac River were running out of numbers. The only way to free up numbers was to end the partial overlay arrangement, a decision that was made in 1991.