least team runs per game given up in a season since 1920 to 2019

Between the 1920 and 2019 seasons, the Baltimore Orioles had the fewest runs allowed per game pitched by a team in a season, with 2.79 in 1972.

	TEAM	R/G	R	G	SEASON	W%	W	L	GS	ERA	SO	CG	SHO	SV	IP	H	ER	HR	BB	HBP	IBB	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	H/9
1	Orioles	2.79	430	154	1972	.519	80	74	154	2.53	788	62	18	21	1371.2	1,116	386	85	395	15	52	5,493	35	5.17	2.59	1.99	0.56	14.3	7.2	1.10	.245	2.82	7.32
2	Cardinals	2.91	472	162	1968	.599	97	65	162	2.49	971	63	27	32	1479.0	1,282	409	82	375	28	62	6,006	30	5.91	2.28	2.59	0.50	16.2	6.2	1.12	.264	2.87	7.80
3	Athletics	2.95	457	155	1972	.600	93	62	155	2.58	862	42	15	43	1417.2	1,170	406	96	418	19	41	5,718	29	5.47	2.65	2.06	0.61	15.1	7.3	1.12	.248	2.90	7.43
4	Tigers	3	492	164	1968	.636	103	59	164	2.71	1,115	59	16	29	1489.2	1,180	449	129	486	32	40	6,043	38	6.74	2.94	2.29	0.78	18.5	8.0	1.12	.246	2.97	7.13
5	Astros	3.01	331	110	1981	.555	61	49	110	2.66	610	23	13	25	990.0	842	293	40	300	11	24	4,034	36	5.55	2.73	2.03	0.36	15.1	7.4	1.15	.261	3.01	7.65
6	Cardinals	3.01	473	157	1943	.682	105	49	157	2.57	639	94	20	15	1427.0	1,246	407	33	477	18		5,841	20	4.03	3.01	1.34	0.21	10.9	8.2	1.21	.260	2.98	7.86
7	Dodgers	3.02	490	162	1966	.586	95	67	162	2.62	1,084	52	13	34	1458.0	1,287	425	84	356	27	67	5,941	42	6.69	2.20	3.04	0.52	18.2	6.0	1.13	.274	3.02	7.94
8	White Sox	3.03	491	162	1967	.549	89	73	162	2.45	927	36	17	39	1490.1	1,197	406	87	465	58	46	6,074	54	5.60	2.81	1.99	0.53	15.3	7.7	1.12	.245	2.97	7.23
9	Mets	3.06	499	163	1968	.451	73	89	163	2.72	1,014	45	17	33	1483.1	1,250	449	87	430	45	67	6,028	59	6.15	2.61	2.36	0.53	16.8	7.1	1.13	.261	3.03	7.58
10	Orioles	3.07	497	162	1968	.562	91	71	162	2.66	1,044	53	15	31	1451.0	1,111	429	101	502	46	42	5,864	53	6.48	3.11	2.08	0.63	17.8	8.6	1.11	.242	3.08	6.89
11	Cardinals	3.08	480	156	1942	.688	106	48	156	2.55	651	70	18	15	1410.1	1,192	399	49	473	19		5,800	31	4.15	3.02	1.38	0.31	11.2	8.2	1.18	.248	3.06	7.61
12	White Sox	3.09	501	162	1964	.605	98	64	162	2.72	955	44	16	45	1467.2	1,216	444	124	401	31	42	5,910	49	5.86	2.46	2.38	0.76	16.2	6.8	1.10	.248	3.07	7.46
13	Indians	3.11	504	162	1968	.534	86	75	162	2.66	1,157	48	20	32	1464.1	1,087	432	98	540	53	64	5,966	42	7.11	3.32	2.14	0.60	19.4	9.1	1.11	.240	3.10	6.68
14	Cardinals	3.12	490	157	1944	.682	105	49	157	2.67	637	89	26	12	1427.0	1,228	424	55	468	22		5,838	13	4.02	2.95	1.36	0.35	10.9	8.0	1.19	.252	3.09	7.74
15	Dodgers	3.14	509	162	1968	.469	76	86	162	2.69	994	38	20	32	1449.1	1,293	433	65	414	37	79	5,951	43	6.17	2.57	2.40	0.40	16.7	7.0	1.18	.277	3.16	8.03
16	White Sox	3.17	517	163	1966	.512	83	79	163	2.68	896	38	19	34	1475.1	1,229	440	101	403	36	55	5,982	68	5.47	2.46	2.22	0.62	15.0	6.7	1.11	.248	3.15	7.50
17	Orioles	3.19	517	162	1969	.673	109	53	162	2.83	897	50	19	36	1473.2	1,194	463	117	498	22	55	5,972	34	5.48	3.04	1.80	0.71	15.0	8.3	1.15	.243	3.16	7.29
18	Yankees	3.21	343	107	1981	.551	59	48	107	2.90	606	16	0	30	948.0	827	305	64	287	10	17	3,872	25	5.75	2.72	2.11	0.61	15.7	7.4	1.18	.263	3.26	7.85
19	Dodgers	3.22	521	162	1965	.599	97	65	162	2.81	1,079	58	17	35	1476.0	1,223	461	127	425	33	53	6,018	51	6.58	2.59	2.54	0.77	17.9	7.1	1.12	.252	3.18	7.46
20	Indians	3.23	504	156	1954	.721	111	43	156	2.78	678	77	12	38	1419.1	1,220	439	89	486	16		5,866	13	4.30	3.08	1.40	0.56	11.6	8.3	1.20	.246	3.20	7.74
21	Dodgers	3.24	356	110	1981	.573	63	47	110	3.01	603	26	15	24	997.0	904	333	54	302	14	38	4,099	19	5.44	2.73	2.00	0.49	14.7	7.4	1.21	.272	3.21	8.16
22	Yankees	3.24	531	164	1968	.512	83	79	164	2.79	831	45	11	27	1467.1	1,308	455	99	424	30	62	6,032	27	5.10	2.60	1.96	0.61	13.8	7.0	1.18	.260	3.26	8.02
23	Cardinals	3.24	525	162	2015	.617	100	62	162	2.94	1,329	1	0	62	1464.2	1,359	478	123	477	45	37	6,134	48	8.17	2.93	2.79	0.76	21.7	7.8	1.25	.297	3.23	8.35
24	Giants	3.25	529	163	1968	.543	88	74	163	2.71	942	77	19	16	1468.2	1,302	442	86	344	24	87	5,990	56	5.77	2.11	2.74	0.53	15.7	5.7	1.12	.265	3.24	7.98
25	White Sox	3.25	527	162	1968	.414	67	95	162	2.75	834	20	4	40	1468.0	1,290	448	97	451	66	69	6,080	40	5.11	2.76	1.85	0.59	13.7	7.4	1.19	.258	3.23	7.91