74LS181: Maximum output current?
The outputs are limited to 400uA  (sourcing) if you need it to have valid logic levels in order to drive TTL-level inputs with guaranteed noise margins. 

You can load it quite a bit harder if you don't care about connecting it to inputs and are only driving an LED. But as @Tim says, it's better to sink current with the output and have the LED "on" when the output is low- 8mA with guaranteed logic levels and noise immunity. If you have a red LED, you're going to have no more than about 3.2mA for the LED (less for other visible colors) so it can drive a few inputs as well. 

See, for example, this datasheet: 



You did not damage your chip by connecting an LED from outputs through 1K to ground, if the chip  is indeed damaged something else did it.