To understand climate change, it is essential to analyse long time series of atmospheric data. Here we studied the atmospheric pressure observed at Trieste (Italy) from 1841 to 2018. We examined the available information on the characteristics and elevations of the barometers and on the data sampling. A basic data quality control was also applied. As a result, we built a homogeneous time series of daily mean pressures at mean sea level, from which a trend of 0.5 hPa per century was estimated.