One data set I've used as a proxy for extreme events is the state records for hottest and coldest days, and wettest/driest years, 200 records in all. Two caveats: First, the smaller number of recording locations prior to 1900 will bias against representation from that time. Second, some of the temperature extremes note "also on earlier dates", which may also bias against earlier years. (Or not - Maine's hottest temp is one of the ties, but the earlier date occurred during the same week and location.)
There are only 10 records set prior to 1890 and only one of those was for temperature. Then the 1890s, 1900s, and 1910s averaged 9 per decade. The 1920s set only 3 extremes. Then came the 1930s, with 23 record highs, 10 lows, 2 wettest, 17 driest, 52 extremes in all and top decade for all but wettest year. The next six decades averaged 17 each, ranging from 12 to 26. Extremes have been less common during the new millenium, with only 7 for 2000 on, though there may be updated records of which I'm not aware. The two most recent are both cold extremes, 2009 in Maine and 2011 in OK.