Source - SMW
At 52.0 in August, the seasonally adjusted Markit final US Manufacturing Purchasing Managers Index dropped from 52.9 in July but remained comfortably above the neutral 50.0 value. 

The latest PMI reading was fractionally lower than the earlier 'flash' estimate of 52.1 and signalled a weaker improvement in overall business conditions than the average since the survey began in late-2009 (54.0).